1. Start by preparing the crust. Mix all-purpose flour, sugar, and salt in a large bowl. Add cubed cold butter and blend until the mixture resembles coarse crumbs.
2. Gradually add ice-cold water, one tablespoon at a time, mixing just until the dough holds together.
3. Form the dough into a disk, wrap it in plastic wrap, and chill in the refrigerator for at least 30 minutes.
4. Preheat the oven to 375°F (190°C) and line a baking sheet with parchment paper.
5. On a floured surface, roll the chilled dough into a large circle, approximately 12 to 14 inches in diameter.
6. Spread a thin layer of basil pesto or Dijon mustard over the dough, leaving a 2-inch border untouched.
7. Spread dollops of ricotta cheese evenly over the pesto or Dijon base.
8. Arrange thinly sliced heirloom tomatoes over the ricotta in a circular pattern, slightly overlapping the slices.
9. Sprinkle fresh herbs, such as basil, chives, or mint, over the tomatoes. If desired, add shredded cheese for extra flavor.
10. Gently fold the edges of the dough over the filling, creating pleats to hold the shape.
11. Brush the exposed dough edges with olive oil or a beaten egg for a golden finish during baking.
12. Place the galette in the freezer for 20 to 30 minutes to help it maintain its shape while baking.
13. Bake the galette in the preheated oven for approximately 25 to 40 minutes, or until the crust turns golden brown and the center is set.
14. Remove the galette from the oven and let it cool slightly on a wire rack.
15. Before serving, garnish the galette with a drizzle of olive oil, a sprinkle of Parmesan cheese, and additional fresh herbs.
16. Serve the Tomato Ricotta Galette warm or at room temperature and enjoy its rustic and flavorful taste.