Tennessee Onion Casserole

Baked potato and sweet onion casserole topped with melted cheese in a glass baking dish.

Tennessee onion casserole is a cheesy Southern side dish made with thinly sliced sweet onions, cheddar, Gruyère, and Parmesan. Baked with butter, fresh thyme, and smoky seasoning, it’s a flavorful addition to holiday dinners or Sunday supper.

Course Side

Cuisine American

Keyword cheesy onion casserole, sweet onion casserole, Tennessee onions

Prep Time 15

Cook Time 1 15

Total Time 1 30

Servings

Calories 215kcal

Author Kat Jeter & Melinda Machado

Ingredients

3 pounds Sweet onions
2 tablespoons Olive oil
2 teaspoons Salt
2 teaspoon Brown sugar
1 teaspoon Black pepper
1 teaspoon Smoked paprika
1 teaspoon Garlic powder
1 teaspoon Mustard powder
1 teaspoon Fresh thyme finely chopped
½ teaspoon Cayenne pepper
4 ounces Shredded cheddar cheese
4 ounces Shredded Gruyere
½ cup Parmesan Cheese
3 tablespoons Butter

Instructions

Preheat oven to 350 degrees F. Spray a 9x13 inch baking dish with non-stick spray.
Thinly slice the onions, preferably with a mandoline to get the thinnest slices.
Add the onion slices to a large bowl and drizzle the olive oil on top. Toss the onion slices in the olive oil.
In a small bowl combine the salt, brown sugar, black pepper, smoked paprika, garlic powder, mustard powder, thyme, and cayenne pepper. Mix well.
Sprinkle the seasoning over the onions and toss until well coated.
Spread half of the onion slices in a 9x13 inch baking dish and top with 2 ounces of shredded cheddar and 2 ounces of shredded Gruyere.
Add the remaining onion slices and top with remaining cheddar and Gruyere cheese.
Top with the grated Parmesan cheese.
Cut the 3 tablespoons of butter into small pieces and dot it over the top of the casserole.
Cover the dish tightly with foil and place in the oven to cook for 45 minutes.
After 45 minutes carefully remove the foil from the dish and continue to bake for 30 minutes more.
Remove from oven and serve hot.

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