Tennessee Onions

Category:Soups, Stews & Chili

The moment the foil comes off, the cheese is bubbling and the edges are just starting to turn golden. Underneath, the onion rings have softened in their own juices and the butter, ready to scoop up with that stretchy, savory topping. That’s what I want from Tennessee Onions: tender, sweet onions with a browned cheese layer, not a pan of crisp onions hiding under cheese.

I keep the onions in an even layer and give them a covered start before uncovering the dish. The first stretch lets the rings soften without asking the cheese to brown too soon; the uncovered finish gives the top time to bubble and pick up color. It’s a straightforward oven side, but that switch from covered to uncovered makes the difference between firm onions and a soft, scoopable pan of Tennessee onions.

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Kitchen Note

Give the pan the full 5-minute rest before serving. The bubbling calms down, and the melted cheese settles onto the onions instead of sliding away when you scoop.

Save Tennessee Onions for a cozy dinner side: sweet, tender onion rings under a bubbly, golden cheese topping.

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Why Tennessee Onions Steam Before They Brown

Sweet onions give up moisture as they bake. That’s useful here: the tightly covered first part of baking traps steam around the rings, so they soften before the cheese has to take on much color. Without that covered start, the exposed cheese can darken while the thicker onion pieces still have a firm bite.

Once the foil comes off, the goal changes. The moisture can escape, and the cheese has direct oven heat to turn bubbly and lightly browned. This isn’t a dry-roasted onion dish, and a little liquid in the bottom of the pan is normal. What you’re looking for is an onion ring that yields easily when pierced, with a top that’s melted and lightly golden rather than deeply browned or crisp. Keeping the rings spread evenly helps the thicker pieces get their share of heat, too. If you pile them in a mound, some will soften more slowly while others are already tender.

How Sweet Onions and Three Cheeses Share the Pan

Tennessee Onions bubbling cheese topping

Sweet onions — Their mild sweetness stands up to the savory cheese without making the dish sharp or pungent. Choose firm onions without soft spots; the even 1/4-inch rings help them cook at a similar pace.
Butter and dried seasonings — Small pieces of unsalted butter melt across the onions, while garlic powder, Italian seasoning, oregano, salt, and pepper season the whole pan. Unsalted butter gives you better control over the seasoning, and ordinary dried herbs work well here.
Mozzarella and sharp cheddar — Mozzarella brings the stretchy melt, while sharp cheddar adds a more pronounced savory bite. Pre-shredded cheese is convenient and works, though cheese shredded at home usually melts into a smoother layer.
Finely grated Parmesan — Fine shreds scatter through the other cheeses instead of landing in heavy clumps, adding a salty, savory note across the top. A finely grated version is more useful here than large flakes.

From Raw Onion Rings to a Bubbly, Browned Top

Set Up the Onion Layer

Heat the oven to 350°F and lightly coat a 9×13-inch baking dish with nonstick cooking spray. Peel the sweet onions and slice them into 1/4-inch rings, keeping the thickness as even as you can. Arrange the rings evenly in the dish rather than packing them into a high mound. That gives the heat a better chance to reach the whole layer.

Season Before Adding the Cheese

Scatter the butter pieces over the onion rings, then sprinkle on the garlic powder, Italian seasoning, dried oregano, kosher salt, and black pepper. Spread the seasonings around the dish so one area doesn’t get a concentrated pinch of herbs or pepper. The butter melts as the onions bake, carrying those savory seasonings around the pan. Don’t stir the rings into a pile; keep the layer even.

Cover for the Tender First Bake

Sprinkle the mozzarella, sharp cheddar, and finely grated Parmesan evenly over the onions. Cover the baking dish tightly with foil and bake for 30 minutes. When you uncover it, expect softened onions and melted cheese, but don’t look for a browned top yet. If the rings still feel firm in the middle at this point, that’s why the dish gets an uncovered finish next.

Uncover Until the Cheese Is Bubbly

Remove the foil and bake for 10 to 15 minutes more. Check the thickest onion ring with a fork: it should be tender when pierced, not crunchy or resistant. The cheese should be bubbling and lightly browned, especially around the edges. Pull the dish once both cues are there rather than waiting for a deeply browned crust.

Three Ways to Shift the Cheese Without Losing the Onion Base

Lean into sharp cheddar

Use a larger share of the sharp cheddar and a smaller share of the mozzarella, keeping the Parmesan in the mix. The topping tastes tangier and less stretchy, so keep the cheese spread evenly to cover the onions.

Make the herbs more oregano-forward

For a more direct oregano flavor, leave out the Italian seasoning and keep the dried oregano. You’ll lose the extra blended-herb notes, but the onions and cheese still make a full, savory pan.

Make it dairy-free

Replace the butter with plant-based butter, then use dairy-free mozzarella-style and cheddar-style shreds plus a vegan Parmesan-style topping in the same amounts as the listed cheeses. The onion base will still soften, though plant-based cheeses often melt less smoothly and may brown differently from dairy cheese.

Storage and Reheating

Refrigerator: Refrigerate leftovers within 2 hours and store them in an airtight container for 3 to 4 days. The onions soften further, and the cheese won’t be as stretchy after chilling.
Freezer: Freeze in an airtight freezer-safe container for up to 2 months for best quality. The onions will be softer and may release extra liquid after thawing; thaw overnight in the refrigerator.
Reheating: Reheat in a 325°F oven, covered, until the center reaches 165°F. Uncover for the last few minutes if you want to refresh the browned cheese; prolonged high heat can make the cheese greasy.

Questions That Come Up Once the Dish Is in the Oven

Can I make Tennessee Onions with yellow onions?+

Yes. Yellow onions work, but they taste sharper and less sweet than the sweet onions used here. The cheese and seasoning still pair well with them, so expect a more savory, less mellow result.

How do I prep Tennessee Onions ahead of time?+

Slice the onions up to a day ahead and keep them covered in the refrigerator. You can also cut the butter and measure the seasonings ahead, but assemble the dish shortly before baking so the cut onions don’t sit under the cheese and release liquid into the pan.

Can I use frozen sliced onions instead of fresh?+

Fresh onions are the better choice for this dish. Frozen onions thaw soft and release more moisture, so they’re less likely to hold distinct rings and can leave the finished pan wetter than intended.

Can I double the batch in one baking dish?+

I wouldn’t pile a doubled batch into one 9×13-inch dish; the deeper layer can cook unevenly. Divide it between two 9×13-inch dishes instead, and watch the onions and cheese closely near the end since two pans in the oven may brown at a different pace.