01 - In a mixing bowl, combine the ground beef, basil pesto, minced garlic, kosher salt, and black pepper. Gently fold the mixture until just incorporated, being careful not to overwork the meat. Divide into 4 equal portions and shape into uniform patties, pressing a slight dimple in the center of each to prevent puffing during cooking.
02 - Whisk together the mayonnaise, finely minced garlic, fresh lemon juice, and chopped parsley in a small bowl. Season with salt and pepper to taste. Cover and refrigerate to allow the flavors to meld while you cook the burgers.
03 - Preheat a grill or cast-iron skillet over medium-high heat. Place the burger buns cut-side down and toast for 1 to 2 minutes until golden brown and lightly crisped. Remove and set aside.
04 - Place the patties on the preheated grill or skillet and cook for 4 to 5 minutes per side, or until they reach your preferred doneness. During the final minute of cooking, lay a slice of provolone or mozzarella cheese atop each patty and cover with a lid or foil to melt the cheese.
05 - Spread a generous layer of creamy garlic mayo on the bottom half of each toasted bun. Layer on a lettuce leaf, followed by the cheesy patty, a tomato slice, and red onion rings. Add an extra spread of mayo on the top bun if desired, then close the sandwich.
06 - Serve the burgers immediately while hot, alongside your choice of sides such as crispy fries, a fresh salad, or roasted vegetables.