1. Start by peeling and slicing the Tennessee onions into even 1/4-inch rings. Uniform slices help them cook evenly, which is something I learned the hard way during my early kitchen blunders.
2. In a large skillet, heat the olive oil over medium heat until shimmering. Add the butter if you’re using it—this combo gives the onions a perfect balance of flavor and mouthfeel.
3. Add the sliced onions to the skillet, spreading them out evenly. Sprinkle with kosher salt and pepper to draw out moisture and season the layers.
4. Cook the onions, stirring occasionally, for about 10 minutes until they start to soften and turn translucent. This is the moment I always pause to smell the kitchen and remind myself that good things take time.
5. Sprinkle the brown sugar over the onions to boost caramelization, then continue cooking for another 10-15 minutes, stirring every few minutes to prevent burning. You’re looking for a rich golden color and a sweet, mellow aroma.
6. Once caramelized, splash the apple cider or balsamic vinegar over the onions and stir well. This brightens the flavor and adds a subtle tang that elevates the dish.
7. If using, toss in fresh thyme or rosemary sprigs during the last few minutes of cooking to infuse herbal notes.
8. Remove from heat, discard the herb sprigs, and serve warm.

One tip I learned hosting those college dinners is to keep an eye on the heat—too high and the onions burn, too low and they stew rather than caramelize. Medium heat and patience are your best friends here.