2 cups all-purpose flour
1 tablespoon baking powder
1 3/4 teaspoons salt, divided
3/4 stick (6 tablespoons or 3 ounces) cold unsalted butter, cut into 1/2-inch cubes, plus 2 teaspoons melted
3/4 cup whole milk
1/3 cup mayonnaise
2 tablespoons fresh lemon juice
1 3/4 pounds beefsteak tomatoes
1 1/2 cups corn (from about 3 ears), coarsely chopped by hand (my preference) or lightly puréed in a food processor, divided
2 tablespoons finely chopped basil, divided (skipped this, no harm was done)
1 tablespoon finely chopped chives, divided
1/4 teaspoon black pepper, divided
7ounces coarsely grated sharp Cheddar (1 3/4 cups), divided
Whisk together flour, baking powder, and 3/4 tsp salt in a bowl, then blend in cold butter (3/4 stick) with your fingertips or a pastry blender until it resembles coarse meal. Add milk, stirring until mixture just forms a dough, then gather into a ball.
Divide dough in half and roll out one piece on a well-floured counter (my choice) or between two sheets of plastic wrap (the recipe’s suggestion, but I imagined it would annoyingly stick to the plastic) into a 12-inch round (1/8 inch thick). Either fold the round gently in quarters, lift it into a 9-inch pie plate and gently unfold and center it or, if you’re using the plastic warp method, remove top sheet of plastic wrap, then lift dough using bottom sheet of plastic wrap and invert into pie plate. Pat the dough in with your fingers trim any overhang.
Preheat oven to 400°F with rack in middle. If your kitchen is excessively warm, as ours is, go ahead and put the second half of the dough in the fridge until you’re ready to use it. Whisk together mayonnaise and lemon juice.
slice tomatoes crosswise 1/4 inch thick and, if desired, place on towel and sprinkle with salt. let sit for 30 min or more. Spread 1 tbsp dijon on crust. Spread a small amount of cheese on crust then Arrange half of tomatoes in crust, overlapping, and sprinkle with half of corn, basil, chives, salt, 1/8 teaspoon pepper and one cup of grated cheese. Repeat layering with remaining tomatoes, corn, basil, chives, salt, and pepper. Pour lemon mayonnaise over filling and sprinkle with remaining cheese.
Roll out remaining piece of dough into a 12-inch round in same manner, then fit over filling, folding overhang under edge of bottom crust and pinching edge to seal. Cut 4 steam vents in top crust and brush crust with melted butter (2 teaspoons). Bake pie until crust is golden and filling is bubbling, 30 to 35 minutes, then cool on a rack. Serve warm or at room temperature.
Do ahead: Pie can be baked 1 day ahead and chilled. Reheat in a 350°F oven until warm, about 30 minutes.
An idea: Want to slab pie this and serve it to a crowd? I agree, it would be brilliant. This is how I’d approach it: Make 1 1/2 batches of the crust (slab pies require more crust for the same amount of filling) and arrange the filling in one layer instead of two in a parchment-lined 15x10x1-inch pan. Increase the amount of butter you brush the top with to a tablespoon or two and the baking time to about 45 minutes (this is an estimate, you should take it out when it is golden and the filling is bubbling). Be sure to remove the tomato seeds; that extra wetness could make for a slab pie mess.