Ingredients:

  • 3 large Vidalia or Walla Walla sweet onions (approx. 2 lbs), peeled and sliced into 1/4-inch rings
  • 0.5 cup unsalted butter, cut into small cubes
  • 1 tsp garlic powder
  • 1 tsp dried oregano
  • 0.5 tsp dry mustard powder
  • 1 tsp kosher salt
  • 0.5 tsp cracked black pepper
  • 1 cup extra sharp yellow cheddar, freshly grated
  • 1 cup Monterey Jack cheese, freshly grated
  • 0.5 cup grated Parmesan cheese

Instructions:

  1. Preheat and Prep. Set your oven to 350°F and lightly grease your 9x13 baking dish with butter or non stick spray.
  2. Slice the Onions. Cut the 3 large sweet onions into 1/4 inch rings. Note: Keep them uniform so they cook at the same rate.
  3. Arrange the Base. Separate the rings and layer them evenly in the prepared dish. They should fill the dish about three quarters of the way up.
  4. Season the Layers. Sprinkle the 1 tsp kosher salt, 0.5 tsp black pepper, 1 tsp garlic powder, 1 tsp oregano, and 0.5 tsp dry mustard evenly over the onions.
  5. Add the Butter. Distribute the 0.5 cup of cubed butter across the top of the seasoned onions. Watch for even coverage so every onion gets bathed in fat.
  6. The First Cheese Layer. Sprinkle the 1 cup of Monterey Jack and 1 cup of extra sharp cheddar over the buttered onions.
  7. The Parmesan Finish. Top everything with the 0.5 cup of grated Parmesan. Note: This creates the protective lid that browns beautifully.
  8. Bake the Casserole. Place in the oven for 35 minutes until the cheese is bubbling and mahogany brown.
  9. Rest the Dish. Let it sit for 5 minutes before serving. Note: This allows the juices to settle and the cheese to firm up slightly.