Step 1

In a large skillet, heat 1 tablespoon of olive oil over medium-high heat. Add the onion; cook until lightly browned on the edges (about 6 minutes). Transfer onion to a large bowl and set aside to cool completely.

Step 2

Line 2 baking sheets with paper towels. Place sliced tomatoes in a single layer on the paper towels. Sprinkle with 1 teaspoon salt. Allow to sit for 30 minutes to remove some of the moisture, then pat dry with additional paper towels.

Step 3

Once the onion is cool, stir in Swiss cheese, 1 cup of the cheddar, mayonnaise, basil, pepper, egg and ½ teaspoon salt.

Step 4

Spread half of the mayonnaise mixture in the bottom of the prepared crust. Sprinkle with 1 tablespoon bread crumbs. Arrange half of the tomatoes on top (overlapping slightly). Repeat with another layer of the mayonnaise mixture, another layer of breadcrumbs, and another layer of tomatoes. Sprinkle remaining ½ cup of cheddar cheese over top.

Step 5

Bake in a 350 degree F oven for about 45 minutes, or until brown and bubbly.

Step 6

Cut into slices and serve warm or at room temperature. I find that it's easiest to slice when I allow the pie to rest for at least 20 minutes being cutting into it.