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 indentation in the center to prevent puffing during cooking.
02 - In a small bowl, whisk together the mayonnaise, finely minced garlic, fresh lemon juice, and chopped parsley. 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 the internal temperature reaches 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 a lettuce leaf, followed by the cheesy patty, a tomato slice, and a few red onion rings. Add additional mayo to the top bun if desired, then close the burger.
06 - Serve the burgers immediately while hot, paired with your choice of side dishes such as fries, a green salad, or roasted vegetables.