Burgers with Mozzarella and Spinach-Arugula Pesto

Ingredients

• 10 cups baby spinach packed
• 2 large beefsteak tomatoes cut into 1/4-inch-thick rounds
• 2  garlic clove peeled
• 1.8 pounds ground beef 20% ( fat)
• 0.5 teaspoon pepper black
• 6  hawaiian rolls split
• 1 teaspoon juice of lemon fresh
• 0.5 teaspoon lemon zest packed finely grated ()
• 6.3 inch mozzarella fresh
• 0.3 cup olive oil extra virgin extra-virgin
• 3 tablespoons parmesan cheese packed freshly grated ()
• 3 tablespoons pinenuts 
• 1 pinch pepper dried red crushed
• 1 teaspoon salt 

Equipment

• bowl
• grill
• microwave

Directions

1. Rinse spinach; drain briefly, then place in large glass bowl. Microwave spinach, uncovered, on high just until wilted, 1 to 1 1/2 minutes.
2. Drain, then squeeze out as much liquid as possible.
3. Combine garlic, lemon peel, and crushed red pepper in processor; blend until garlic is finely chopped.
4. Add spinach, 2 cups (packed) arugula, pine nuts, and lemon juice; process until coarse puree forms. With machine running, gradually add oil in thin stream and blend until almost smooth.
5. Mix in cheese.
6. Transfer pesto to small bowl; season with salt.
7. Do ahead: Can be made 6 hours ahead. Cover; chill.
8. Combine ground beef, 1 teaspoon salt, 1/2 teaspoon black pepper, and 6 tablespoons spinach-arugula pesto in large bowl; mix lightly with fingertips or fork just until incorporated. Form meat mixture into six 3/4-inch-thick patties.
9. Place patties on platter.
10. Do ahead: Beef patties can be made 6 hours ahead. Cover and refrigerate.
11. Prepare barbecue (medium-high heat). Grill burgers to desired doneness, about 4 minutes per side for medium-rare. Grill buns, cut side down, just until lightly toasted, about 1 minute. Build burgers with pesto, patties, mozzarella cheese, tomatoes, and arugula. Cover with bun tops.