- 2 1/2 cups chopped sweet onion (such as Vidalia®)
- 2 cups mayonnaise (such as Hellman's®)
- 2 cups shredded mozzarella cheese
- salt and ground black pepper to taste
- Preheat oven to 350 degrees F (175 degrees C).
- Stir onion, mayonnaise, and mozzarella cheese together in a casserole dish; season with salt and pepper.
- Bake in the preheated oven until top is beginning to brown, 25 to 30 minutes.