Serves a Crowd

Caramelized Onion and Butternut Squash Tart

January 24, 2016
5 Stars
Photo by James Ransom
Author Notes

This decadent tart is packed with caramelized onions, roasted butternut squash, Gruyère and crème fraîche. It makes an excellent vegetarian main or a rich, savory side. —Vanessa Larson

Test Kitchen Notes

WHO: Vanessa Larson is a brand-new member of the Food52 community. Welcome!
WHAT: A rich, salty, savory tart with as much melty cheese as there are roasty onions and squash.
HOW: Caramelize onions with butter and thyme, then combine with roasted squash in a pre-baked tart shell. Pour a cheesy, savory custard over the vegetables and bake until bubbly and golden.
WHY WE LOVE IT: Caramelized onions, roasted butternut squash, Gruyère, and crème fraîche—it literally could not be bad. We like the addition of whole wheat flour to the crust, as it adds a little extra heft. Our only complaint is that we ate too much of the squash before putting it in the tart—maybe the recipe should suggest roasting extra? (Just kidding. Mostly.) —The Editors

Watch This Recipe
Caramelized Onion and Butternut Squash Tart
  • Serves 6 to 8 as a main
  • Caramelized Onion and Butternut Squash Tart
  • 1 recipe pastry dough (see below)
  • 1 large butternut squash, peeled, seeded, and cubed
  • 1 tablespoon olive oil
  • 2 large yellow onions, halved and sliced
  • 3 tablespoons unsalted butter
  • 2 eggs
  • 8 ounces crème fraîche
  • 4 ounces Gruyère, grated
  • 2 ounces Parmesan, grated
  • 1 teaspoon sea salt
  • 1 teaspoon freshly ground black pepper
  • 4 sprigs thyme
  • Pastry Dough
  • 3/4 cup all-purpose flour
  • 1/2 cup whole wheat flour
  • 1/4 teaspoon salt
  • 1 stick butter
  • 4 tablespoons ice water
In This Recipe
  1. Caramelized Onion and Butternut Squash Tart
  2. Melt butter in large saucepan over medium heat. Add onions, thyme sprigs, and 1/2 teaspoon salt, stirring to mix. Cover and reduce heat to low. Cook, stirring occasionally, until dark golden brown, about 45 minutes. Remove thyme stems.
  3. Meanwhile, preheat oven to 450° F. Toss butternut squash with olive oil and 1/2 teaspoon salt and spread out on baking sheet. Bake until browned and very soft, stirring once, about 40 minutes.
  4. Reduce oven heat to 350° F. Roll dough out until thin and press into a well-greased 10-inch tart pan. Prick all over with a fork and bake in oven 10 minutes.
  5. In a medium mixing bowl, combine eggs, crème fraîche, gruyère, Parmesan, and black pepper.
  6. Spread caramelized onions in bottom of tart and top with butternut squash. Pour gruyère mixture over the squash, making sure to spread it evenly throughout the tart.
  7. Bake until golden brown and cooked through, about 30 to 40 minutes.
  1. Pastry Dough
  2. Cut butter into 1-tablespoon pieces and freeze for 10 minutes.
  3. Mix flour and salt in food processor or large bowl.
  4. If using food processor, add butter and mix until mixture resembles small pea-sized balls. If mixing by hand, work quickly, mixing the butter in with your hands until it forms small pea-sized balls.
  5. Add in ice water and mix just until dough forms and comes together. Form into disk, wrap in plastic, and place in fridge for 20 minutes.
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60 Reviews

Shelley April 8, 2022
Fabulous! I did add an extra egg as the custard was not ‘pourable’. I’m sure it’s was pilot error..perhaps because the marscapone was super thick or because I finely grated the Gruyère.. I also did not have wheat flour and use all purpose. This worked fine.
I will definitely make again!
Shelley April 8, 2022
Meant to say crème fraiche..not marscapone!
Josephsm December 17, 2021
Wow, this got quite a good reception from my guests. It's something different, yet not unfamiliar. I followed the recipe except I substituted rye flour for the wheat flour and that worked fine. I also added cayenne pepper to the custard to counterbalance the sweetness of the onions and squash and I think that worked well. Definite make-again dish.
Melanie November 24, 2021
Made this for office pot luck and it was delicious! For creme fraiche, I used equal parts whole fat greek yogurt and heavy cream. Yummy and easy!
epicharis October 22, 2021
Just superlative. Fixed this with a koginut squash and couldn't have been happier. Unbelievably rich---you need a nice sharp or floral wine to cut this.
rox L. December 4, 2020
Delicious even with the error I made. I got ahead of myself and missed the blind baking of the crust. This recipe is a keeper and I will definitely be making this again. I served the tart as part of our Thanksgiving meal.
Alicia October 15, 2020
This is just so delicious. Very rich, very decadent. And SO tasty!
glammie October 12, 2020
Made this today and it was phenomenal, despite a few mishaps on my part. I used store-bought 8" shell because I completely forgot the recipe called for a 10" crust. Also, I disagree with covering the pan when caramelizing the onions. Mine went a little mushy before they were fully browned and I think that was due to condensation.

I cooked the onions and squash the night before and refrigerated. Couldn't find creme fraiche at two stores so used full-fat sour cream. Assembled quickly the next day. Was sooooooo delicious. A keeper! Next time I might add a little green -- sautéed kale or spinach or leftover roasted broccoli.
Suzy Q. March 3, 2021
Great review..and good tip on the condensation. Thanks!
Debbie November 3, 2019
I made this and it was amazing! Followed the recipe exactly EXCEPT I was too lazy to make the crust so I used a frozen deep dish pie shell. Oh. My. Goodness. My family devoured it and I plan on making this again for Thanksgiving. May even give the homemade crust a shot. Thanks for sharing the recipe for this incredibly delicious dish.
msfrost75 November 3, 2019
Amazing flavour, I’ll make this again for sure. I substituted The creme fraiche for thick Greek yogurt and it worked great. I love the caramelized onions on this tart, which I will add to other tarts I make!
Amy October 29, 2019
I have never had my husband rave about something I've cooked EVER. And he (supposedly hates BN squash). I caramelized the onions ahead of time in the slow cooker so I'd have a lot of them to use for other things. Then I just heated them up in the pan with the thyme right before assembling the tart. I used refrigerated pie crust and an ungreased ceramic quiche baking dish. It turned out wonderful and didn't stick. Highly recommend.
Marlene March 1, 2018
Has anyone tried substituting the crème fraiche with sour cream ? if so, how did it turn out ? thanks
Annie April 9, 2019
Yes, I used half sour cream and half yogurt. It worked well!
cosmiccook October 6, 2019
sour cream will separate stick w creme fraiche.
glammie October 12, 2020
I made this today with full fat sour cream. It was ah-may-zing. I have extra of all the ingredients; making it again this week.
Mary November 29, 2017
Make this outstanding tart twice, following the directions exactly the first time. Heavenly! The second time, I added a big bunch of spinach, traded half and half for the creme fraiche, and used swiss cheese. Sooooo good!!
JPolly September 18, 2017
I made this, but it overflowed a 10 inch tart pan. I think a 10 in pie pan, or an 11 inch tart pan would be better. I didn't like the hunks of squash in the creamy filling--and I cut very small hunks--plus IMHO the taste of the butternut squash got lost trying to compete with all those yummy onions and cheeses. My son suggested removing the squash and adding in bacon, which I am going to try next (i'm not a vegetarian, obviously!) and since the filling is sooooo rich, I think individual mini quiches might be the way to go--more pastry to deal with the almost overwhelming rich filling. Good recipe but not perfect--but odd with the hunks of squash, and too much filling for a 10 inch tart pan.
nutcakes November 21, 2017
It's a good idea to stop pouring when it overflows the pan! 10 inch tart pan is deeper than 10 inch pie pan, unless your pie pan is deep dish, I think. Cook any extra filling in a small pan or mug. Usually for a quiche-like dish I would fill a pan 3/4. Sweet squash is a classic paring with Gruyere.
cosmiccook October 19, 2019
I made this again for the 3rd time. I had leftover caramelized onions &apples from another recipe on this site. I used 1/2 creme fraiche & 1/2 Goat and used Trader Joes Sea Coast cheddar and added french herbs to the mix. I lacked 2 tbsp. of whole wheat so I made up the diff. w Pecan meal and added Quatre Epices to both dough and batter.
What wasn't specified was the depth of the tart pan--there are some pans referred to as tart/quiche pans that are 2" high. This works well w the 11" pan I have that is 1" high.
Siouxchef February 2, 2017
Oh, and someone else commented that goat cheese would make a nice addition. The Dahlia Lounge recipe did have 1/4 cup goat cheese.
Siouxchef February 2, 2017
Hi, Vanessa. Did you get this recipe from the Dahlia Lounge in Seattle? I've had this recipe for years and it was attributed to the Dahlia Lounge.
Vanessa L. February 2, 2017
No, I did not! I am not even sure who Dahlia Lounge is. I originally made this for vegetarian family, based it on other tart recipes, and used butternut squash because it was in season.
Siouxchef February 2, 2017
OK, Vanessa. Same ingredients, same order, same technique. Just a big coincidence. Really, there are no "unique" recipes any more. They're all built on someone else's framework.
Vanessa L. February 2, 2017
The technique is one that is used in almost all savory tarts and the ingredient combination is hardly revolutionary. If this was inspired by someone else, I would have given them credit as I have with other recipes. However, it's pretty hard to pilfer the recipe of someone you have never heard of. I agree that there are not unique recipes - we all inspire each other. I'm lucky enough to be inspired by all I eat, cook and discover. Hope you have a great day and find you own inspiration.
tessga January 14, 2017
this was so so good.
David S. November 27, 2016
I made one with left over puff pastry the bottom was a little thin but over a great filling mix
Cbrady November 27, 2016
I have extra pie shells from thanksgiving. Can I bake a pie crust and then bake per tart instructions? It sounds great!
cosmiccook November 16, 2016
how much approx. in cubed squash please? 2-3 cups?
cosmiccook November 15, 2016
To make less sweet added garlic, herbs Provence and quatre épices to give it a little umph & a small grind of birds eye pepper. final deglaze of onion w a balsamic. Voila!