Spray a skillet with cooking spray and place it over medium-high heat. Add 1/2 of a medium sweet onion, thinly sliced. Saute the onion until soft and golden brown, adding apple cider as needed to prevent burning.

Lay 2 slices of sourdough bread on a clean surface. Layer with a small Granny Smith apple that’s thinly sliced, some Brie cheese, and the onions. Cover with 2 more slices of bread (this makes 2 sandwiches).

Spray the skillet with more cooking spray. Grill the sandwiches until the cheese melts and the bread browns. Cut the sandwiches in half and serve.