Ingredients

Serves 6

　　1 large red onion

　　2 pounds ground beef

　　3/4 cup dried tomato and arugula pesto, or to taste

　　6 ounces mozzarella, cut into 6 slices

　　olive oil for brushing onion

　　6 hamburger buns, grilled lightly if desired

　　

For the pesto:

1 1/2 cups packed arugula, washed well and spun dry

　　1/3 cup drained bottled dried tomatoes packed in oil

　　1/4 cup olive oil

　　3 tablespoons freshly grated Parmesan

　　2 tablespoons pine nuts, toasted golden and cooled

　　1 large garlic clove, chopped and mashed to a paste with 1/2 teaspoon salt

　　a pinch sugar

　　

To make the cheeseburgers:

Step 1

Prepare grill.

　　

Step 2

Cut six 1/4-inch-thick slices from center of onion and reserve. Divide beef into 6 portions. Form indentation in each portion and spoon rounded teaspoon pesto into each indentation. Form beef portions into six 3/4-inch-thick patties, enclosing pesto completely. Grill patties on an oiled rack set 5 to 6 inches over glowing coals 5 minutes. Turn burgers and grill 3 minutes more. Top burgers with mozzarella and grill 2 minutes more, or until just cooked through. Transfer burgers to a platter and let stand while grilling onion. Brush onion on both sides with oil and grill until softened and browned, about 3 minutes on each side.

　　

Step 3

Spread pesto on both sides of buns and make sandwiches with onion and burgers.

　　

To make the pesto:

Step 4

In a food processor blend together all ingredients with salt and pepper to taste until smooth. Pesto keeps, surface covered with plastic wrap, chilled, 1 week. Makes about 1 cup.