Caramelized Onion and Apple Panini

Name: Caramelized Onion and Apple Panini
Cuisine: European, American, Italian, Mediterranean
Ingredients: 4 Slices Martin’s Cinnamon-Raisin Swirl Potato Bread; 1 Tablespoon Fresh Sage, chopped; 6 Tablespoons Butter, room temperature, divided; 1 Granny Smith Apple, thinly sliced; 2 Large Yellow Onions, thinly sliced; 4 Ounces Cheddar Cheese, finely shredded; 2 Ounces Brie Cheese; 2 Teaspoons of Kosher Salt