2 cups all-purpose flour
1 1/2 teaspoons baking powder
1/2 teaspoon baking soda
1/2 teaspoon kosher salt
6 tablespoons (3/4 stick) chilled unsalted butter, cut into 1/2" cubes
1 cup buttermilk
2 pounds large ripe tomatoes, cored and cut into 1/4" slices
2 1/2 cups coarsely grated extra-sharp cheddar (8–9 ounces)
1/4 cup finely grated Parmesan (1/2 ounce)
1 scallion, trimmed, chopped
1/2 cup mayonnaise
2 tablespoons chopped fresh dill
1 tablespoon apple cider vinegar
2 teaspoons sugar
3/4 teaspoon kosher salt
1/2 teaspoons freshly ground black pepper
1 1/2 tablespoons cornmeal
Special Equipment: Use a 9"-diameter glass or ceramic pie dish