Ingredients for Crust
1 cup all-purpose flour
½ teaspoon kosher salt
1 stick cold unsalted butter (1/4 pound), cut in 1/8-inch pieces
3 tablespoons ice water
Ingredients for Tarte Filling
5-7 eggs, whisked
1 teaspoon salt
2 tablespoons Dijon mustard
Sliced or shredded gruyere cheese (enough to cover the bottom of the tarte crust)
2-3 Tomatoes, sliced
Herb de Provence
Put flour and salt in the bowl of a stand mixer or food processor. Add butter and quickly cut it into flour until mixture resembles coarse meal. Add ice water and mix briefly, about 30 seconds, to form a soft dough. Remove dough, shape into a thick disk, wrap in plastic and refrigerate for at least 2 hours. Bring to cool room temperature before rolling.
To roll, lightly flour dough and counter. Roll out gradually, periodically letting dough rest for a moment before continuing. This makes rolling easier and will keep dough from shrinking back during baking.
Roll dough to a thin round approximately 13 inches in diameter, then lay dough in your tarte pan, letting it relax a bit. Fold the edges back inside to make a double thickness, then press firmly against the pan so the finished edge is slightly higher than the pan.
Broil the slices of tomatoes on a greased cooking sheet, sprinkling each generously with herb de provence and salt. They should get soft and caramelize slightly on the edges.
Preheat oven to 350 degrees
Whisk the eggs and the salt together in a bowl and set aside. Once the crust is in the pan you can gently spread the Dijon mustard over the bottom and then lay or sprinkle the Gruyere cheese on top of that. Pour in the egg mixture into the crust and bake for approximately 30 minutes, or until it is browned on top and done in the middle. At about 15 minutes in, take the tart out and arrange the broiled slices of tomatoes into the tarte. Place the tarte back into the oven to cook for the remaining time.