Baked Ziti with Spinach and Tomatoes

This is a recipe that both my husband and I absolutely love. Here's what you need:

3/4 lb. of hot Italian sausages, casings removed (I use half of a Turkey Kielbasa instead)
1 medium onion, chopped
3 large garlic cloves, chopped
1 28 oz. can of diced, peeled tomatoes
1/4 C of purchased pesto sauce
10 ounces ziti or penne pasta (about 3 cups), freshly cooked (I usually use the whole box)
8 C ready-to-use spinach leaves (about 2/3 of a 10 ounce package)
6 oz. mozzarella cheese, cubed
1 C grated Parmesan cheese (about 3 oz.)
Salt and pepper

Directions
Heat a heavy large saucepan over medium-high heat. Add sausage, onion and garlic and saute' until sausage is cooked through, breaking up the meat with a the back of a spoon (about 10 minutes). Add tomatoes with juices to the pan. Simmer until the sauce thickens slightly, stirring occasionally, about 10 minutes. Stir in pesto. Season with salt and pepper. (This part can be prepared one day ahead. Cover and refrigerate. Bring to a simmer before continuing.)

Preheat oven to 375 degrees. Lightly oil a 13x9 inch glass baking dish. Combine cooked pasta, spinach, mozzarella and 1/3 C of Parmesan cheese in a large bowl. Stir in hot tomato sauce. Transfer the mixture to the prepared baking dish. Sprinkle the remaining 2/3 Parmesan cheese over the top. Bake until sauce bubbles and cheeses melt (about 30 minutes).

[Recipe compliments of Carmela M. Meely, via Epicurious]