Tomato Slab Pie with Bacon and Herbs

For the Tomato Slab Pie: 

Line a baking sheet with two layers of paper towels. Cut the stem ends off the tomatoes, then gently squeeze out as many seeds as possible. Slice the tomatoes to a thickness of ¼ inch. Place the tomatoes on top of the paper towels in a single layer and sprinkle with salt. Layer more paper towels on top of the tomato slices and repeat with remaining tomatoes. Let sit at room temperature for at least one hour or up to five hours.

Cook the bacon over medium heat in a large skillet until it is crisp, about 8 minutes. Use a slotted spoon to remove the bacon from the skillet, and place it on a paper towel-lined plate. Remove all but 1 tablespoon of the bacon fat from the skillet.

Add the onion to the same skillet and cook over medium-low heat until it is soft and caramelized, about 30 minutes. 

Preheat the oven to 350 degrees. Beat the egg in a small bowl, then stir in the mayonnaise and dry mustard. Once combined, stir in the cheeses. 

Line the bottom of the prepared pastry crust with 1/3 of the tomatoes, then season them with salt and pepper. Top with half the onions, then half the bacon, then half the chopped herbs. Spread half the egg-cheese mixture over. Repeat with another 1/3 of the tomatoes and the remaining onions, bacon, herbs, and cheese. Top the pie with a single layer of sliced tomatoes. 

Bake the pie for 40 minutes, or until the top begins to brown and bubble. Let it sit for at least 10 minutes before serving. Serve warm, at room temperature, or cold, sprinkled with some more of the chopped herbs.

For the Pastry Crust:

Put the flour into the container of a food processor. Add the butter and pulse. When the mixture resembles coarse meal, add the egg yolk. Continue pulsing while gradually adding the water. Add enough water so that the dough will come away from the sides of the container and be firm but pliable enough to shape into a ball. Flatten the ball of dough a little to make a disk, then wrap it in plastic wrap. Chill for 30 minutes. 

Preheat the oven to 400 degrees. Line an 8-by-8-inch baking pan with parchment, making sure some hangs over the sides of the pan. Lightly flour your countertop, and use a rolling pin to roll the dough out to about a 1/8-inch thick square. Carefully transfer the crust to the prepared baking pan, using your hands to make it fit. You will have about ½ inch of dough go up the sides of the pan. Don’t worry about that being too perfect. Refrigerate for 30 minutes.

Line the crust with parchment paper and fill it with dried beans or pie weights. Bake 10 minutes.

Remove the parchment and beans or weights. Brush very lightly with beaten egg.