Cook spaghetti according to package directions. Meanwhile, heat oil in a large saucepan over medium heat. Add onion and garlic; cook, stirring occasionally, 6 to 8 minutes or until onion is tender. Add tomatoes, olives, capers, anchovy paste and pepper flakes; bring to a boil over high heat. Reduce heat; simmer 5 minutes. Stir in sausage; simmer 5 minutes. Drain spaghetti; transfer to 4 shallow bowls. Stir fresh mozzarella cheese into sausage mixture; serve over spaghetti and top with basil.

Makes 4 servings