Preheat the oven to 325 degrees Fahrenheit.
Bake the deep dish frozen pie crust for 5 to 8 minutes.
Peel and slice the tomatoes.
Sauté the chopped onion in olive oil until softened.
In a mixing bowl, combine the mayonnaise, beaten egg, and grated sharp cheese until the mixture is smooth.
Layer the sliced tomatoes in the pie shell, seasoning them with salt and pepper.
Top the tomatoes with the sautéed onions.
Spread the mayonnaise mixture evenly over the onions and tomatoes, reaching the edges of the pie shell.
Place the pie on the bottom rack of the oven and bake for 30 minutes.
Crush the Ritz crackers and mix them with the melted butter to create a topping.
Sprinkle the cracker topping over the pie and bake for an additional 15 minutes.
