Makes 3 sandwiches
1/2 of a large onion, sliced in 1/4 inch slices
1 apple, Granny Smith or Honey crisp, to your taste, cored and sliced in 1/4 inch thick matchsticks
1/2 Tbsp unsalted butter plus more to grill sandwiches
salt and pepper
4 ounces sharp cheddar, grated, divided into 3 equal...