Knead basil pesto into ground beef before grilling
Light a grill and oil the grates. Grill the burgers over moderately high heat for 3 minutes. Flip the burgers, top them with the mozzarella slices and close the grill. Cook for 3 minutes longer for medium-rare burgers. Grill the buns until lightly toasted, then spread some of the pesto on the bottoms. Top with the burgers, the tomatoes, mozzarella and the remaining pesto. Close the burgers and serve right away.