1lbsweet italian sausageremoved from casings if necessary
1/4-1/2tspred pepper flakes
28ozcan diced tomatoesundrained
Heat olive oil over medium heat. Sauté onions until translucent, about 2-4 minutes. Add garlic and cook about 30 seconds. Add sausage and break apart into small pieces while browning, about 5 minutes. Season to taste with red pepper flakes.
Meanwhile, cook pasta according to package directions.
When sausage is browned, add undrained tomatoes and heavy cream. Bring to a simmer.
Mix cornstarch with cold water to make a slurry, then add slowly to sauce, stirring constantly. Cook until thickened. Stir in pasta and spinach.