Rinse spinach, drain briefly, then place in large glass bowl. Microwave spinach, uncovered, on high just until wilted, 1 to 1 1/2 minutes. Drain, then squeeze out as much liquid as possible. Combine garlic, lemon peel and crushed red pepper in processor; blend until garlic is finely chopped. 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 smooth. Mix in cheese. Transfer pesto to small bowl, season with salt.
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 until just incorporated. Form meat mixture into six 3/4-inch patties. Place patties on platter.

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.

You can visit Local-Edition for more videos like this. We have more recipes and videos there.