1 cup mayonnaise
2 cups shredded Swiss cheese
1/2 cup grated Parmesan cheese
2 cups thinly sliced Vidalia sweet onion
hot sauce, or to taste
Preheat oven to 350 degrees F (175 degrees C).
Stir the mayonnaise, Swiss cheese, Parmesan cheese, Vidalia onion, and hot sauce together in a casserole dish.
Bake in the preheated oven until the edges are golden brown, 30 to 35 minutes. Allow to cool 10 minutes before serving.