From Gouda to Cheddar, homemade pickled red onions, and a crispy Parmesan-encrusted exterior... There's a reason we called the ultimate grilled cheese.

The Ultimate Grilled Cheese

Prepare Pickled Red Onion: Combine red onion, olive oil, red wine vinegar, and oregano leaves in a small bowl. Season with salt and pepper. Cover and let stand for 2 hours. Drain. Refrigerate up to 1 week. Makes 1 cup.

Combine mayo and pest; set aside. Spread butter on bread. Sprinkle Parmesan cheese on butter; gently press into bread.

Layer 3 tablespoons Cheddar cheese, 1 slice Guda, half of pesto mixture, 3 slices salami, 2 tomato slices, 1/4 cup arugula, 2 tablespoons Pickled Red Onions, 2-1/2 tablespoons Cheddar cheese, and 1 slice Gouda between 2 bread slices with buttered sides on outside. 

Preheat a nonstick skillet over medium-low heat. Place sandwich in skillet; weigh it down with a heavy lid. Grill 3 to 4 minutes on each side or until toasted and cheese is melted. Repeat for remaining sandwiches. 