Spread the mayonnaise on the insides of the buns. Add the onion confit. Add sliced salami to two of the bun halves.
Cut the apple into thin slices. Garnish each sandwich with a few slices and top with cheddar and provolone. Assemble the sandwiches [U1] and butter the tops and bottoms of the buns.
Heat a skillet over medium heat. Grill for 4 to 6 minutes on each side, or until the bread is golden and the cheese is cooked. For a crispier texture, place a plate on top of each sandwich during cooking.
Serve immediately accompanied with fresh salad.
For a more heightened gourmet experience, replace the sliced apples with sliced pickles!