INGREDIENTS
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MAKES 1 10-INCH PIE 2 HOURS, 30 MINUTES
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For the pie crust
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1 1⁄4 cups all-purpose flour
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2 1⁄2 tsp. granulated sugar
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1⁄2 tsp. salt
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6 tbsp. cold butter cut into 1⁄2-inch cubes
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2 tbsp. plus 1 tsp. ice-cold water
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1⁄2 tsp. white vinegar
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For the filling and topping
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3 1⁄2 lb. vine-ripe tomatoes (about 12), cored, seeded, and cut into 1⁄2-inch dice, divided
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2 tsp. salt, divided
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1 tsp. sugar, divided
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1 tbsp. butter
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1 large yellow onion, thinly sliced with the grain
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1 tsp. picked thyme
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2 tbsp. extra-virgin olive oil
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1⁄4 tsp. freshly ground black pepper
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1⁄3 cup packed whole basil leaves
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1⁄2 cup mayonnaise
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1⁄3 cup grated fontina
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1⁄3 cup grated Parmigiano-Reggiano
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2 large Roma or heirloom tomatoes, thinly sliced and blotted dry with paper towels