Prepare the dough: In a large bowl, combine the gluten-free all-purpose flour, cornmeal, and salt. Add the cold, cubed butter. Use your fingers or a pastry cutter to cut the butter into the flour until the mixture looks like coarse crumbs.

Add the apple cider vinegar and cold water, starting with 3 tablespoons of water. Stir until the dough comes together. If needed, add an additional tablespoon of water.

Gather the dough into a ball, flatten into a disk, wrap in plastic wrap, and refrigerate for at least 1 hour.

Prepare the ricotta filling: In a bowl, combine the ricotta, parmesan cheese, finely chopped parsley, minced or grated garlic, 1/4 teaspoon of salt, and black pepper. Mix until well combined. Set aside.

Prepare the tomatoes: Slice the heirloom tomatoes and cut the cherry tomatoes in half. Set them aside.

Preheat your oven to 400°F (205°C).

Assemble the galette: Roll out the chilled dough between two pieces of parchment paper into a 12-inch circle.

Remove the top parchment paper. Spread the ricotta filling over the dough, leaving a 2-inch border around the edges.

Arrange the sliced heirloom tomatoes and cherry tomatoes over the ricotta filling. Drizzle with olive oil, then sprinkle the remaining 1/4 teaspoon of salt and the black pepper over the tomatoes.

Gently fold the edges of the dough over the tomatoes, pleating as needed to make the galette shape.

Prepare the egg wash: In a small bowl, beat together the egg and 1 teaspoon of water. Brush the egg wash over the dough edges.

If your kitchen is warm, you can put the galette into the refrigerator for 15-20 minutes before baking to let the butter solidify again.

Bake the galette for about 35-40 minutes, or until the crust is golden brown and the tomatoes are roasted and the pastry is golden brown.

Remove from the oven and allow it to cool for about 15 minutes.

Before serving, garnish with fresh basil leaves. This galette is delicious served warm or at room temperature.