01 - In a mixing bowl, combine 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 - Whisk together 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. Remove and set aside.
04 - Place the patties on the hot grill or skillet and cook for 4 to 5 minutes per side, or until the internal temperature reaches your desired doneness. During the last minute of cooking, lay a slice of provolone or mozzarella cheese on 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 red onion rings. Add an extra spread of mayo on the top bun if desired, then close the burger.
06 - Serve the burgers immediately while hot, paired with your favorite side dishes such as fries, coleslaw, or a crisp green salad.