Southern Tomato Pie | Saveur

Ingredients

• 1 1⁄4 cups all-purpose flour
• 2 1⁄2 tsp. granulated sugar
• 1⁄2 tsp. salt
• 6 tbsp. cold butter cut into 1/2-inch cubes
• 2 tbsp. plus 1 tsp. ice-cold water
• 1⁄2 tsp. white vinegar
• 3 1⁄2 lb. vine-ripe tomatoes (about 12), cored, seeded, and cut into 1⁄2-inch dice, divided
• 2 tsp. salt, divided
• 1 tsp. sugar, divided
• 1 tbsp. butter
• 1 large yellow onion, thinly sliced with the grain
• 1 tsp. picked thyme
• 2 tbsp. extra-virgin olive oil
• 1⁄4 tsp. freshly ground black pepper
• 1⁄3 cup packed whole basil leaves
• 1⁄2 cup mayonnaise
• 1⁄3 cup grated fontina
• 1⁄3 cup grated Parmigiano-Reggiano
• 2 large Roma or heirloom tomatoes, thinly sliced and blotted dry with paper towels