Step 1

Make the crust: Add the cheese crackers to the bowl of a food processor. Pulse for 20–30 seconds, until the crackers are broken down into crumbs.

Step 2

Add the flour, salt, and pepper to the food processor and blend for 20–30 seconds to incorporate into the cracker crumbs.

Step 3

Add the butter and cheddar cheese and blend for 30–60 seconds, until the butter is broken down into pea-sized pieces.

Step 4

Transfer the mixture to a medium bowl. Add the apple cider vinegar and 3 tablespoons of cold water and mix with your hands to combine. Add more water, 1 tablespoon at a time, until the mixture holds together well, feels slightly damp, and does not crumble when pressed.

Step 5

Shape the dough into a disc and tightly wrap in plastic wrap. Chill in the refrigerator for 1 hour.

Step 6

Preheat the oven to 375˚F (190˚C).

Step 7

Lightly dust a clean surface and a rolling pin with flour. Set the chilled dough on the floured surface and begin to roll out the dough, starting from the center and working your way outwards, applying even pressure. The fewer passes of the rolling pin over the dough, the more tender the crust will be. Rotate the dough as you roll it out, using a bench scraper, as necessary to keep the dough from sticking to the surface. If the dough begins to feel sticky, lightly dust with more flour. Roll the dough out to ⅛- to ¼-inch (3 mm - 6 mm) thick. The dough should be wide enough to fit into a 11-inch (27 cm) tart pan with some excess dough overhanging.

Step 8

Wrap the dough around the rolling pin and transfer to the tart pan, gently draping it over. Press the dough down into the bottom of the pan and up the walls. Roll the rolling pin over the top of the pan to trim the edges. Transfer the tart crust to the refrigerator to chill while you cut out dough strips for the top.

Step 9

Gather the excess dough into a ball. Shape the dough in a rectangle and roll out to about 4 inches wide (10 cm) and 12 inches (30 cm) long, ⅛- to ¼-inch (3 mm - 6 mm) thick. Using a pastry cutter, trim off any excess dough so you are left with an even rectangle. Cut out ¼-inch and ½-inch-wide (6 mm - 12 mm) strips of dough. Transfer dough strips to plate and transfer to the refrigerator while you fill the tart crust.

Step 10

Remove the tart pan from the refrigerator and spread the mustard over the bottom of the crust. Cover the bottom of the crust with the cheddar cheese. Add a layer of tomato slices, overlapping slightly. Sprinkle with ¼ teaspoon of salt, ¼ teaspoon pepper, ½ tablespoon of thyme, and half of the shallots. Repeat with a second layer of tomatoes and the remaining ¼ teaspoon salt, ¼ teaspoon pepper, ½ tablespoon thyme, and shallots.

Step 11

Remove the dough strips from the refrigerator, and create a decorative lattice design over the tart.

Step 12

Brush the beaten egg all over any exposed dough, including the edges around the tart pan.

Step 13

Bake the tart for 40–45 minutes, until the crust is a deep golden brown and crisp to the touch.

Step 14

Let the tart cool for 20 minutes to allow the tomato juices to absorb.

Step 15

Serve with a dollop of sour cream and fresh thyme leaves.

Step 16

Enjoy!