Line baking sheets with paper towels. Place tomato slices on prepared pans; sprinkle with 1 teaspoon (3 grams) salt. Let stand at room temperature for 30 minutes; pat dry. Let stand for 30 minutes; pat dry.

On a lightly floured surface, roll Cheesy All-Butter Pie Dough into a 13-inch circle (about ⅛ inch thick). Transfer to a 9-inch deep-dish pie plate, pressing into bottom and up sides. Trim edges to ½ inch beyond edge of plate. Roll edges under, and crimp as desired. Freeze for 15 minutes, or refrigerate for 30 minutes.

Position oven rack in bottom third of oven. Preheat oven to 425°F (220°C).

In a medium bowl, stir together cheese, onion, mayonnaise, sliced basil, egg, pepper, and remaining 1 teaspoon (3 grams) salt. Spread half of cheese mixture (about 300 grams) in bottom of prepared crust. Layer half of tomato slices in an overlapping pattern on top of cheese mixture in crust. Top with remaining cheese mixture; top with remaining tomato slices.

Bake until golden brown, center is set, and an instant-read thermometer inserted in center registers 175°F (80°C), 40 to 45 minutes, covering crust with foil after 25 to 30 minutes of baking to prevent excess browning. Let cool completely. Serve at room temperature. Garnish with basil leaves, if desired. Cover and refrigerate for up to 2 days.