1. Prepare grill or broiler.
2. Heat a large nonstick skillet over medium heat. Coat pan with cooking spray. Add the pancetta to pan; cook 4 minutes or until crisp. Remove pancetta from pan, reserving drippings in pan; set pancetta aside. Add onion and garlic to pan; cook 5 minutes or until softened, stirring frequently. Combine onion mixture, pepper, salt, seasoning, and beef in a bowl. Shape beef mixture into 8 (1/4-inch-thick) patties. Top each of 4 patties with pancetta and 2 tablespoons Swiss cheese, leaving a 1/4-inch border around edge. Top with remaining 4 patties; pinch edges to seal.
3. Place patties on grill rack or broiler pan coated with cooking spray; cook 5 minutes. Turn and cook 5 minutes or until a meat thermometer inserted in center measures 160°. Combine mayonnaise and pesto. Spread about 1 tablespoon of the mayonnaise mixture on bottom half of each bun. Top each serving with 1 patty and top half of the hamburger bun.