• 3 tablespoons salted butter
• 2 yellow onions, thinly sliced
• kosher salt and black pepper
• 3/4 cup apple cider
• 1 tablespoon fresh thyme leaves
• 1 tablespoon chopped fresh sage
• 1 pinch crushed red pepper flakes
• 4 slices prosciutto (optional)
• 8 slices sourdough bread
• 2 tablespoons extra virgin olive oil
• 1 1/2 cups shredded fontina cheese
• 1 1/2 cups shredded gouda or white cheddar cheese
• 1 honeycrisp apple, thinly sliced  {more}

I am going to let the pictures do the rest – tantalizing much?

{photo and recipe source and credit}