Baked Pasta with Chicken Sausage

Coarse salt and ground pepper
1 tablespoon olive oil
1 medium red onion, chopped
4 cloves garlic, minced
1 can (28 ounces) whole tomatoes with juice, lightly crushed with hands (or crushed tomatoes)
1/2 teaspoon dried oregano
1/2 cup heavy cream
1 pound rigatoni
10 ounces baby spinach (I double the amount of spinach - fresh or frozen)
12 ounces smoked chicken (or turkey) sausage, halved lengthwise and sliced 1/4 inch thick
6 ounces fontina (or mozzarella) cheese, 4 ounces cut into 1/2-inch cubes and 2 ounces coarsely grated
1/4 cup grated Parmesan cheese

Bring a large pot of salted water to a boil. Heat oil in a large skillet over medium heat. Add onion; cook until translucent, about 3 minutes. Stir in garlic. Cook for another minute.Stir in tomatoes and oregano; cook until tomatoes are falling apart, 10 to 15 minutes. Add cream; cook until warmed through, about 5 minutes. Season sauce with salt and pepper.Meanwhile, preheat oven to 400 degrees. Cook pasta in the boiling water until al dente, according to package instructions. Add spinach, and cook just until wilted. Drain, and return contents to pot.Add tomato sauce, sausage, and cubed fontina to pot; toss to coat. Season with salt and pepper. Divide evenly between two shallow 1 1/2-quart baking dishes. Top with grated fontina and Parmesan. Bake until browned and edges are crisp, 20 to 30 minutes.