Caramelized Onion and Butternut Squash Tart

January 24, 2016

Test Kitchen-Approved

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

Food52 Review: 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

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


Caramelized Onion and Butternut Squash Tart

  1. 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.
  2. 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.
  3. 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.
  4. In a medium mixing bowl, combine eggs, crème fraîche, gruyère, Parmesan, and black pepper.
  5. 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.
  6. Bake until golden brown and cooked through, about 30 to 40 minutes.

Pastry Dough

  1. Cut butter into 1-tablespoon pieces and freeze for 10 minutes.
  2. Mix flour and salt in food processor or large bowl.
  3. 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.
  4. 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.

More Great Recipes:
Pie|Tart|Butternut Squash|Cheese|Onion|Thyme|Vegetable|Serves a Crowd|Christmas|Fall|Thanksgiving|Winter

Reviews (43) Questions (1)

43 Reviews

Marlene March 1, 2018
Has anyone tried substituting the crème fraiche with sour cream ? if so, how did it turn out ? thanks
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.
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. <br />
Author Comment
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.<br />
Author Comment
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!<br />
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!
Debbie November 13, 2016
Just made this and it is incredible! 5 stars and 6 thumbs up from me, my husband and son. Will definitely make this for Thanksgiving!
Lisa November 13, 2016
What would be approximately weight of a large butternut squash?
Heidi V. November 11, 2016
Can you make this ahead of time and freeze? Looking for some dishes I can prep before the big Tday.
David S. October 20, 2016
this is one great dish its a keeper
Daniel F. October 7, 2016
Can you buy pastry dough? Would puff pastry work or do you have to make your own?
Lynn S. November 11, 2016
In the first volume of the Vegetarian Epicure, the recipe for Onion Tarte Lyonnaise uses pate brisee - just press it into the pan with your fingers. Comes together in about 10 seconds in the food processor.
Martin B. April 26, 2016
Great recipe. Lovely pastry.<br /><br />It is VERY sweet. But that's no surprise when the two main ingredients are caramelised onion and roast squash. So maybe to be avoided if you don't have a sweet tooth. <br /><br />It could double as a dessert. Especially if paired with something acidic like goat's cheese ice-cream or a strawberry-balsamic compote. Dessert and cheese courses all-in-one!
IslandJulia February 21, 2016
i made this for breakfast this morning (I did some of the prep yesterday, so it came together fast), and it took a lot of self control for us to not finish it in one sitting. Absolutely delicious. Hard pressed to think of a way to enhance it, but maybe a bit of tangy goat cheese. I also like the idea of adding balsamic. But really scrumptious as is.
Author Comment
Vanessa L. February 21, 2016
Glad you liked it! I agree that the balsamic could be a great addition. I also think this would be delicious with roast cauliflower instead of butternut squash!
Nan March 17, 2016
what did you prep the day before <br />
hannahru February 18, 2016
Followed the recipe almost exactly (other than adding balsamic vinegar to the onions)... Came out AMAZING! So savory!! cheese combination was perfect and the crust was wholesome and crusty. Def will be making this again
Author Comment
Vanessa L. February 21, 2016
So glad you liked it!
Bevi February 17, 2016
Author Comment
Vanessa L. February 17, 2016
Thank you!
mrslarkin February 17, 2016
Congratulations, Vanessa!!
Author Comment
Vanessa L. February 17, 2016
Thanks! You're grapefruit tart sounds delicious. Have you ever made it with blood oranges?
mrslarkin February 18, 2016
No, but I bet it would look stunning and taste delicious!