Tomato and cheddar tart with a thyme buttermilk crust

Directions

1. For crust dough
2. In a large mixing bowl, combine both flours, salt, and thyme, and whisk together until well blended
3. Slice the stick of butter into small pats or cubes, dropping each piece into the flour mixture as you go
4. Using a pastry cutter, two forks, or your thumb and forefingers in a pinching and rolling motion, break the slices or cubes of butter up, cutting them in to the flour mixture, until the largest pieces of butter you're seeing are pea-sized. Try to work quickly so that the butter stays as cold as possible. The mix will be extremely dry and crumbly.
5. Make a little well in the center of the mix with your fist. Grate the clove of garlic into the well on the finest side of a cheese grater, or chop finely.
6. Pour all of the buttermilk into the well, and using a rubber spatula gently fold the buttermilk and garlic in with the dry mix. Try and do this with as few turns as possible, since the more you work the dough the tougher it will be. It's especially helpful to use the spatula to get all the way under and pick up any dry flour underneath. If it's still not coming together after a couple of turns, add cold water from the tap one teaspoon at a time until it does.
7. Knead the dough just a couple of times to bring it together. It should feel tacky but not stick to your hands; if it's too wet, add just a little bit of AP flour at a time. Pat the dough into a flat, round disc, wrap tightly in plastic wrap, and place in the freezer while you prepare the filling ingredients, for at least 30 minutes.

1. For the filling
2. Preheat the oven to 450 degrees. Grate the cheeses and mix together in a small bowl so that they're evenly combined together. The mix should be quite salty, but taste to see if you want to add any more salt.
3. Core the tomatoes and slice into the thinnest rounds you can possibly get. I find that a serrated knife works best. If the slices break and aren't full rounds, it doesn't matter -- the tart just looks pretty with slices intact. Lay some folded paper towels or a kitchen towel down and put the slices on top, to drain some of the excess moisture. Peel and slice the shallots or onions into very fine slices as well, like you would to top a burger, either full rounds or "half moon" shapes. Set aside.
4. After you've prepared your filling ingredients or 30 minutes have gone by, whichever comes first, pull your pastry dough from the freezer. It should be firm and stiff but not frozen solid. If it's still very soft, give it another 10 minutes in the freezer.
5. Pour about 1/4 C all purpose flour into a small dish to use for rolling and set on the counter. Flour the counter and set your unwrapped pastry disc on the flour. Flour the top of the disc and the rolling pin as well.
6. Starting from the *middle* of the disc, roll out and away from you with even pressure all the way to the edge of the disc. Give the disc a quarter turn, and repeat. This may seem like a slow way to start, but it helps the dough keep a more circular shape. If pieces of dough break off or make a really craggy outer edge, pull them off and stack them in the middle of the disc to roll again.
7. Continue rolling your pastry until it's about 1/4 inch thick, continuing to flour as you go to keep everything from sticking. The shape doesn't really matter here, the tart will have a rustic look no matter what!
8. Preheat your oven to 450 degrees.
9. Line your baking sheet with a mat or parchment paper. Transfer your rolled out dough to the sheet so that it's laid out on the sheet roughly centered, even though dough may be hanging over the edges for now.
10. Sprinkle the cheese mixture evenly onto the pastry in a circular shape, the largest circle that you can form on your baking sheet while still leaving about 2 inches of pastry dough all around the margins. This will be roughly the shape and size of your tart, so the circle must fit on the sheet itself, even though most likely the dough will be hanging off the sheet right now.
11. Arrange slices of shallots or onion on top of the cheese, evenly spread out, most likely you'll only have enough to make one layer.
12. Arrange the slices of tomatoes on top of the cheese and shallots, in a single layer so that no tomatoes are overlapping. Then, make a second layer of tomatoes on top of the first layer with any remaining tomatoes. Stay as close to that circular shape you outlined at first with the cheese as possible.
13. Fold the edges of the uncovered pastry over and onto the filling, making a circular shape. You do want to "trap" the filling under the lip of the pastry, making a sturdy and roughly circular shape that will hold all the filling in while baking.
14. Bake the tart for an hour and 15 minutes, or until the edges are deeply brown and crisp, the filling is bubbling, and some of the tomatoes on the top are browned. The tart will be very hot when it comes out, so let it cool for a good 15 minutes before slicing and serving.
15. Tart will keep well in the fridge for a few days, and can easily be re-heated in the oven at a low temperature to re-crisp the crust, or be eaten cold.