1- In a medium bowl, combine the flour, sugar, and salt. Whisk to blend these dry ingredients evenly.

2- Add the cold butter pieces to the flour mixture. Using a pastry cutter or your fingers, cut the butter into the flour until the butter pieces are about ¼ inch in size. The mixture should resemble coarse crumbs with some pea-sized butter pieces still visible.

3- Add the grated cheddar and mozzarella cheeses to the mixture. Toss gently to distribute the cheese throughout the flour-butter mixture.

4- In a small bowl, combine the apple cider vinegar with cold whole milk or ice water. Drizzle this liquid over the flour mixture, tossing gently with a fork just until the dough begins to come together.

5- Turn the dough out onto a lightly floured surface. Gather it into a ball, kneading just a few times until it holds together. Be careful not to overwork the dough.

6- Roll out the dough to a rough circle about ¼ inch thick. Fold the dough into thirds, then fold into thirds again in the opposite direction. This creates layers for a flakier crust.

7- Roll the folded dough again to a circle about 12 inches in diameter. Transfer the dough to a parchment-lined baking sheet and refrigerate for 15 minutes to allow the gluten to relax.

8- Preheat your oven to 375°F (190°C) with the rack positioned in the center. This ensures even baking for your heirloom tomato ricotta galette.

9- Remove the chilled dough from the refrigerator. Spread the ricotta cheese evenly over the dough, leaving a 1-inch border around the edges. This border will be folded over the filling.

10- Wash and dry the heirloom tomatoes. Slice them about ¼ inch thick and blot dry with paper towels to remove excess moisture. This step is crucial for preventing a soggy crust.

11- Arrange the sliced heirloom tomatoes over the ricotta in a single layer, overlapping slightly. Scatter the cherry or grape tomatoes around the larger slices.

12- Drizzle the olive oil and honey evenly over the tomato layer. This sweet-savory combination will caramelize beautifully during baking.

13- Fold the edges of the dough over the tomatoes, creating a rustic border. Crease the dough as needed to secure the folds. The center of the galette should remain exposed.

14- Brush the folded crust with the lightly beaten egg. This will give your galette a beautiful golden finish when baked.

15- Place the baking sheet in the preheated oven and bake for 45 to 55 minutes, or until the crust is golden brown and crisp, and the tomatoes are tender.

16- Remove the galette from the oven and let it cool for 30 to 45 minutes before serving. This cooling time allows the filling to set and makes for cleaner slices.

17- Just before serving, sprinkle the remaining coarse Kosher salt and fresh thyme sprigs over the top. The heirloom tomato ricotta galette with honey thyme can be served warm or at room temperature.