Three Cheese Manicotti

1 package manicotti pasta shells (or 14 shells)
1 pound ricotta cheese
1 pound mozzarella cheese, grated
1/2 cup freshly grated Parmesan cheese
1 large egg, beaten
1 10 ounce package frozen spinach, thawed and squeezed dry
1/2 teaspoon kosher salt
1/4 teaspoon black pepper
Sauce (see recipe below)

Grease a 13x9x2 baking dish; set aside. Cook manicotti according to package directions; drain and set aside. In a large bowl mix the ricotta cheese, 2 cups mozzarella cheese, 1/2 cup parmesan cheese, egg, spinach, salt, and pepper. Divide mixture into 14 balls. Carefully split manicotti shells open. Shape cheese ball to fit the shell; close shell and lay seam side down in baking dish. Repeat with remaining shells. Pour sauce over shells and top with remaining mozzarella cheese. Bake uncovered at 350° for 30 minutes (until bubbly). Makes 14 servings.

Sauce:

1 medium onion, chopped
2 tablespoons olive oil
1 can tomato paste
3 cans water
1 tablespoon sugar
1 teaspoon salt
1/4 teaspoon pepper
1/2 teaspoon garlic powder

Sauté onions in the olive oil until golden brown. Add remaining ingredients and simmer for 30 minutes.