01 -
Nonstick cooking spray
02 -
4 large Vidalia or sweet onions (roughly 3 pounds), sliced into 1/4-inch rounds
03 -
1 1/2 teaspoons kosher salt
04 -
1 teaspoon dry mustard powder
05 -
1 teaspoon garlic powder
06 -
1 teaspoon smoked paprika
07 -
1/4 teaspoon cayenne pepper (leave out if you prefer mild)
08 -
1 cup shredded mild cheddar cheese (about 4 ounces)
09 -
1 cup shredded smoked Gouda cheese (about 4 ounces)
10 -
1/3 cup grated Parmesan cheese
11 -
4 tablespoons unsalted butter, cut into small pieces
12 -
2 tablespoons chopped fresh parsley for topping (optional)