Grilled Stuffed Tomatoes

Name: Grilled Stuffed Tomatoes
Ingredients: 4 large or 6 medium beefsteak tomatoes (2 1/2 pounds total); 4 ounces low-moisture part-skim or whole milk mozzarella; 1/4 ounce grated Parmesan cheese (about 1 heaping tablespoon); 2 cups cooked white rice or cauliflower rice, thawed if frozen; 1/2 cup store-bought or homemade basil pesto , plus more for serving; 1/2 teaspoon kosher salt; 1/2 teaspoon freshly ground black pepper; 1/8 teaspoon red pepper flakes; 2 to 4 tablespoons pine nuts