The Seasonings You Should Use When Making Tennessee Onions

For the onion lover, it doesn't get much better than Tennessee onions — an umami-rich Southern casserole where sweet Vidalia onions take centerstage supported by a trio of cheeses. It's cheesy and oniony, mellow, and absolutely crave-worthy. If you've ever wished potatoes au gratin could taste more deeply savory, then this dish is for you. But knowing which seasonings make the best Tennessee onions can be a little trickier than you might think. Luckily, most recipes have four spices in common — cayenne, smoked paprika, garlic salt, and mustard powder — a tried-and-true mix that delivers on the quintessential Southern flavors this casserole promises.

A versatile dish, most Tennessee onion recipes call for mild Vidalia sweet onions from Georgia, but you can substitute other sweet varieties like Walla Walla, Maui, Texas 1015s, or mix it up with a winning combo of alliums. The second most important choice is the cheese. While cheddar and Parmesan are consistently present, options for a third cheese choice range from smoked Gouda and Swiss, to mozzarella and even Havarti. The point? All these tweaks allow you to make this casserole your own, influencing its final flavor profile to suit you.

But nothing contributes to Tennessee onions' classic flavor like the seasonings you toss in before baking. While spice choices range from simple salt and pepper all the way to a super-charged, flavor-packed Cajun blend, it's that core of four that really amps up the flavor in this dish.

Each of the spices commonly used in Tennessee onions plays a vital role in building its balanced flavor. The salty, mild pungency of garlic salt boosts the savory with paprika lending a boldly smokey backbone to the soft sweetness of those Vidalias. Then the subtle tanginess of mustard powder brings a lingering depth when suffused with a gently spicy kick of cayenne. Depending on the recipe you're using, this sweet onion casserole's collection of supporting seasonings can also include black pepper, thyme, parsley, and oregano. For those who like their flavors bright, a little lemon zest, along with a squeeze of lemon to mellow out Tennessee onions' intense flavor may be just the ticket, but for those who like things decidedly sweeter, a bit of brown sugar will see you through.

The biggest flavor hack of all comes from a few folks who use Cajun seasoning. Why? Because most Cajun blends have just about everything you need for this Tennessee favorite — all-in-one — saving you time and money. And while Tennessee onions are often thought of as a summer side, showing up at backyard barbecues (they make great burger toppers) and church potlucks (super easy to make), they're also considered special enough for end-of-year holidays. As sides for festive meals, their flavorful goodness intensifies umami in the likes of meat, poultry, fish, potatoes, and even legendary holiday sides like green bean casserole. Just remember to bring extra, because you're gonna run out quick.