- Preheat Oven: Preheat your oven to 375°F (190°C). Grease a baking dish large enough to hold the onions.
- Prepare Onions: Peel the onions and slice them into 1/2-inch thick rounds or wedges. Arrange them in the prepared baking dish.
- Mix Cheese and Seasonings: In a bowl, combine Gruyère, Swiss, Parmesan, garlic powder, thyme, salt, and pepper. If using mayonnaise, stir it in for creaminess.
- Layer Cheese on Onions: Sprinkle the cheese mixture evenly over the onions.
- Prepare Topping: In a small bowl, combine breadcrumbs (or crushed crackers) with melted butter. Sprinkle over the cheese layer for a golden, crunchy finish.
- Bake: Cover the baking dish with foil and bake for 25 minutes. Remove the foil and bake an additional 10–15 minutes until the topping is golden brown and the onions are tender.
- Serve: Let cool for a few minutes, garnish with fresh thyme if desired, and serve warm as a side dish.
Serving and Storage
- Serving: Serve as a side for roast meats, poultry, or as part of a holiday spread.
- Refrigeration: Store leftovers in an airtight container in the refrigerator for up to 3 days. Reheat in the oven at 350°F (175°C) until warmed through.
- Freezing: Not recommended, as the texture of the baked onions and cheese may change when frozen.
Tips
- Choose sweet onions for natural sweetness that balances the richness of the cheeses.
- Gruyère melts beautifully and adds a nutty flavor; you can substitute with fontina if needed.
- For extra crunch, mix a little Parmesan into the breadcrumb topping.
- Mayonnaise is optional; it makes the cheese layer creamier but is not necessary.
- Cook covered first, then uncover to achieve tender onions with a golden topping.
Conclusion
Tennessee Onions are a decadent, flavorful side dish that combines sweet onions, savory cheeses, and aromatic herbs for a comforting and visually stunning addition to any meal. Easy to prepare and always a crowd-pleaser, this recipe is sure to become a staple at your table.
FAQ
Can I use regular yellow onions instead of sweet onions?
Yes, but sweet onions like Vidalia, Walla Walla, or Maui give a milder, naturally sweet flavor that complements the cheeses best.
Can I make this dish ahead of time?
Yes, you can assemble it a few hours in advance and refrigerate until ready to bake.
Can I make it vegan?
Yes, use vegan cheese and a plant-based mayo substitute.
Can I freeze this dish?
Freezing is not recommended because the texture of baked onions and cheese may become watery or grainy upon thawing.
Can I add herbs like rosemary or sage?
Yes, fresh herbs like rosemary or sage can be added for extra aroma and flavor, but thyme is the classic choice.