Southern Sweet Onion Casserole

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Easy Southern Sweet Onion Casserole features caramelized Vidalia onions paired with sour cream and two types of cheese. Topped with buttery Ritz cracker crumbs, this decadent, creamy onion casserole melts in your mouth.

Onion casserole topped with Ritz cracker crumbs in a white dish.

I love the homey goodness of cooked onions, and fried onion rings are a favorite treat. But, this exceptional, creamy onion casserole is the ultimate in onion recipes and quite possibly the best vegetable side dish ever. It’s classic comfort food.

While this southern onion casserole is ideal for Thanksgiving or other special occasions, it’s easy enough for a casual weeknight dinner. It’s also great for a dinner party, especially when you want to serve something a little out of the ordinary.

Here’s what you will need:

Ingredients for onion casserole including cheese and Ritz crackers.

Sweet onions – use Vidalia if you can find them; if not, any sweet onion will work.
Butter – is used for carmelizing the onions. I usually use unsalted butter for cooking.
Sour cream – adds its tangy, creamy goodness to the party.
Mexican blend cheese – includes Monterey Jack, Cheddar, Asadero, and Quesadilla cheeses. You could also use an Italian blend.
Parmesan cheese – adds its intense, nutty flavor and cheesy deliciousness.
Ritz crackers – are crushed to make a fantastic, crunchy, buttery topping.

Here’s how to make it:

Add butter to a large cast-iron skillet over medium heat. When the butter melts, add the sliced onions.

Sliced onions cooking in a cast iron skillet.

Reduce the heat to low and cook the onions uncovered for 90 minutes. Check on them and stir about every 20 minutes.

When the onions are getting close to being done, preheat the oven to 350 degrees F.

Caramelized sliced onions in a cast-iron skillet.

Place half of the onions in a small casserole dish, which has been greased or sprayed with non-stick cooking spray.
Add half the sour cream and spread it out evenly. A small offset spatula or the bottom of a spoon works well for this.

A layer of sour cream on top of a layer of onions in a baking dish.

Sprinkle half the Mexican grated cheese blend in an even layer over the top.
Top with half of the Parmesan cheese and half of the Ritz cracker crumbs.

A baking dish with layers of onions and cheese.

Repeat the layers ending with a layer of Ritz cracker crumbs.

Onion casserole in a baking dish ready for the oven.

Bake uncovered for 25 to 30 minutes or until the mixture is bubbly and the topping is golden brown. Serve immediately.

Onion casserole in a white baking dish garnished with thyme leaves.

Frequently asked questions:

What are Vidalia onions?

Vidalia onions are a unique variety of sweet onions that are only grown in 20 counties around Vidalia, Georgia. They have a mild, sweet taste that develops because of the soil that they are grown in. Vidalias are more perishable and should be stored in the vegetable drawer of your fridge wrapped separately in paper towels.

What type of onion can be substituted for Vidalia onions?

You can use any variety of sweet yellow onions in this recipe. All sweet onions vary slightly in taste, but all become sweeter and more flavorful when they are caramelized. White and red onions tend to have a sharper, more intense, robust flavor.

What to serve with it?

This delectable sweet onion casserole pairs beautifully with simple main dishes such as smoked turkey or baked ham for the holidays. It is also delicious with beef tenderloin, roast chicken, or pork tenderloin.

How to store leftovers?

Leftovers can be stored covered in the fridge for up to four days. I have never tried, but I don’t think they would freeze well.

Leftovers can be reheated in the microwave for about 30 seconds.

What are caramelized onions?

Carmelized onions are cooked low and slow in butter until they become a light golden brown and sugary sweet. The main difference between caramelizing and sauteeing onions is the amount of time it takes to cook them and the temperature of the heat.

You can’t rush the process of caramelizing onions, and it can take up to an hour and a half for them to become perfectly caramelized. But, I can promise you it’s worth every second.

Can you make it ahead?

Yes, for the best results, you can make this casserole up to eight hours ahead, but do not bake it. Cover and store it in the refrigerator. About an hour before you want to serve it, take it out of the fridge to allow it to come to room temperature, and then bake as directed.

Sharon’s tips:

I use a ten-inch cast iron skillet for cooking the onions. It’s ideal because it maintains the heat, and the onions cook perfectly without sticking or burning. A heavy bottom non-stick skillet will also work.
The onions take a long time to caramelize properly. But, the good news, once you get them going, they don’t need to be watched constantly. A quick stir every twenty minutes or so, and you are golden.
Four onions may seem like a lot when you start, but they will shrink down to less than half of their size once cooked.
I used a small round baking dish that was seven and one-half inches wide and two inches deep for this recipe, and it worked perfectly.
The sour cream and cheese amounts may need to be adjusted slightly if your baking dish is larger or smaller than the one I used. If it’s larger, you may need a bit more than the measurements shown.

If you like vegetable casseroles, you might also like these popular make-ahead favorites: Broccoli Cheese Casserole, Southern Squash Casserole, Baked Mushroom Casserole, Cauliflower Cheese Bake, Baked Tomato Casserole, and Southern Sweet Potato Casserole.

If you need more menu ideas, check out all of my side dish recipes here.

★ If you make this recipe, please leave a comment and give this recipe a star rating. I would love to know how you liked it!

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A white baking dish containing an onion casserole.

Southern Sweet Onion Casserole Recipe

Sharon Rigsby

This easy casserole features caramelized sweet Vidalia onions paired with sour cream and two types of cheese, plus a Ritz cracker crust.

4.53 from 17 votes

Print Recipe Pin Recipe

Prep Time 5

Cook Time 2

Total Time 2 5

Course Side Dish

Cuisine American, Southern

Servings servings

Calories 402 kcal

Ingredients

▢ 4 large sweet onions peeled, thinly sliced, and separated (Vidalia, if you can find them)
▢ ½ cup unsalted butter
▢ ½ cup sour cream
▢ ½ cup grated Mexican cheese blend
▢ ½ cup grated Parmesan cheese
▢ 1 cup crushed Ritz crackers (about 24 crackers)

Instructions

Add butter to a large skillet over medium heat. When the butter has melted, add the onions.
Reduce the heat to low and cook the onions uncovered for about 90 minutes. Stir about every twenty minutes.
When the onions are getting close to done, preheat the oven to 350 degrees F.
Place half of the onions in a small casserole dish, which has been greased or sprayed with non-stick cooking spray.
Add half the sour cream and spread out evenly.
Sprinkle half the Mexican grated cheese evenly over the top.
Top with half of the Parmesan cheese and half of the Ritz cracker crumbs.
Repeat the layers ending with a layer of Ritz cracker crumbs.
Bake uncovered for 25 or 30 minutes or until the mixture is bubbly and the topping is golden brown.

Notes

Leftovers can be stored covered in the fridge for up to four days. I have never tried, but I don’t think they would freeze well.

Reheat leftovers in the microwave for about 30 seconds.

You can make this casserole up to eight hours ahead, but for the best results, do not bake it. Instead, cover and store it in the refrigerator. Then, about an hour before you want to serve it, take it out of the fridge to allow it to come to room temperature, and then bake as directed.

I use a ten-inch cast-iron skillet for cooking the onions. It’s ideal because it maintains the heat, and the onions cook perfectly without sticking or burning. A heavy bottom non-stick skillet will also work.

The onions take a long time to caramelize properly. But, the good news, once you get them going, they don’t need to be watched constantly. A quick stir every twenty minutes or so, and you are golden.

Four onions may seem like a lot when you start, but they will shrink down to less than half of their size once cooked.

I used a small round baking dish that was seven and one-half inches wide and two inches deep for this recipe, and it worked perfectly.

The sour cream and cheese amounts may need to be adjusted slightly if your baking dish is larger or smaller than the one I used. If it’s larger, you may need a bit more than the measurements shown.

Nutrition

Calories: 402kcalCarbohydrates: 26gProtein: 11gFat: 37gSaturated Fat: 20gPolyunsaturated Fat: 4gMonounsaturated Fat: 5gCholesterol: 79mgSodium: 378mgPotassium: 223mgFiber: 1gSugar: 8gVitamin A: 950IUVitamin C: 7.4mgCalcium: 330mgIron: 1.1mg

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**This recipe was originally published on November 8, 2017. It was updated and republished on August 24, 2021, with the addition of a “how-to” video, a FAQ section, new photos, and cooking tips. I also increased the number of onions in the original recipe from three to four and the onion cooking time from 30 minutes to 90 minutes.

Comments

4.53 from 17 votes (12 ratings without comment)

Here’s what you will need:

Here’s how to make it:

Frequently asked questions:

Sharon’s tips:

📋 Recipe: