We love this Heirloom Tomato Galette! Wonderfully rustic and a great way to showcase those delicious summer heirloom tomatoes, galettes are easy to make and their free-form assembly makes them look perfectly imperfect.
Slice the tomatoes about 1/4-inch thick and arrange on a large rimmed baking sheet lined with paper towels. Sprinkle with 1 teaspoon of the salt and let stand for 30 to 40 minutes while you make the crust.
Cube the butter, place it in a small bowl and place it in the freezer until firm and very cold, about 10 minutes. In a mixer fitted with the paddle attachment, add the flours, 1/2 teaspoon salt, and the frozen butter. Mix on medium-low speed until the butter is the size of peas, about 3 minutes. Add the water to the mixer in a steady stream and combine until the dough comes together in a moist clump. If it’s too dry to come together after about 30 seconds, add another splash of water.
Transfer the dough to a lightly floured countertop and gather and pat it into a smooth ball. Using a floured rolling pin, roll it out to a 15-inch circle, rotating it occasionally to be sure it isn’t sticking, and dusting with additional flour as needed. Roll the dough up loosely onto the rolling pin and unroll it onto a large, rimmed baking sheet lined with a sheet of parchment paper. Loosely fold in any overhanging edges, cover with plastic wrap, and place the dough in the refrigerator until cold and firm, about 20 minutes.
Preheat the oven to 400˚F.
In a small bowl, combine the feta cheese, goat cheese and the minced oregano. Toss to combine.
Remove the chilled dough from the fridge. Scatter half of the cheese mixture in the center of the dough, leaving a 2-inch border.
Pat the tomatoes as dry as possible and overlap them in an even layer over the cheeses. Add the remaining cheese mixture.
Fold the edges of dough over the filling, overlapping every 4 inches or so to make a pleated crust. Brush the crust lightly with some of the beaten egg. Dust the top of the galette with the flake salt and ground pepper.
Bake the galette until the crust is deep golden and crisp and the tomatoes are lightly browned in spots, 60-75 minutes, rotating the pan halfway through baking. (Some juices may seep onto the baking sheet during baking. This is normal for a rustic galette.) Cool to room temperature.
Garnish with the aged balsamic vinegar and fresh oregano leaves. Cut the galette into wedges to serve.