Make the tart

1. In the bowl of a food processor, pulse the flour, sugar, and salt. Scatter the cold butter pieces and pulse until they are the size of peas. Add the ice water and pulse until the dough comes together. Gather the dough, shape it into a disk, wrap it in plastic and refrigerate for at least 30 minutes. Wash the bowl and blades of the food processor – you’ll need them again.
2. Slice the tomatoes into ½“ slices and place them in a colander, sprinkling lightly with salt as you layer them. Let the tomatoes drain for about 30 minutes.
3. Back to the food processor: blend the ricotta cheese, Dijon mustard, garlic, egg, salt and black pepper until smooth. Stir in the herbs by hand.
4. Preheat the oven to 400°F.
5. On a lightly floured surface, roll out the dough to a 14” circle, and place it into a 10” tart pan. Let the excess dough hang over the edge of the pan. Spread the filling evenly over the bottom of the dough.
6. Line a large plate with several layers of paper towel. Working in batches, transfer the tomatoes from the colander to the paper towels to remove excess moisture. Arrange them in overlapping circles over the tart filling, finishing with a few grinds of pepper. Tuck the excess tart dough around the outside of the tart, shaping it evenly with your fingers as you go; the now double-layer crust edge will rise above the tart ring a bit. You may wish to place it on a baking sheet to catch any drips—bake for 20 minutes.
7. Remove the tart from the oven and sprinkle with the Gruyere cheese (including the crust). Bake until golden brown (30-40 minutes).  Serve warm or at room temperature with a green salad, steamed green beans, or asparagus. Hint: it’s even better the next day, reheated just a touch.