Cook the Pasta: Bring a large pot of salted water to a boil. Add the spaghetti and cook according to the package directions until al dente. Reserve ½ cup of pasta water, then drain the pasta and set aside.
12 oz spaghetti
Cook the Sausage: Heat the olive oil in a large skillet over medium heat. Add the crumbled sausage and cook for about 5 minutes, stirring occasionally and breaking it into small pieces, until browned and fully cooked. Drain excess fat.
1 tablespoon olive oil, 15 oz mild Italian sausage
Add Garlic and Seasonings: To the cooked sausage, add the minced garlic, Italian seasoning, and red pepper flakes. Stir and cook for 1-2 minutes until the garlic is fragrant.
4 cloves garlic, 1 teaspoon Italian seasoning, ¼ teaspoon red pepper flakes
Make the Sauce: Add the marinara sauce to the skillet and stir to combine. Add the fresh spinach and stir again. Cover the skillet and simmer on medium heat for 4-5 minutes, stirring occasionally, until the spinach is wilted.
1 ¾ cups marinara sauce, 6 oz fresh spinach
Add Fresh Tomatoes: Stir the chopped tomatoes into the sauce and cook for an additional 2-3 minutes. Taste the sauce and adjust the seasoning with salt and black pepper as needed.
4 medium tomatoes, Salt and black pepper to taste
Combine with Pasta: Add the cooked spaghetti to the skillet with the sauce. Toss everything together to coat the pasta evenly. If the sauce is too thick, add a splash of the reserved pasta water to reach your desired consistency.
Garnish and Serve: Remove the skillet from heat. Sprinkle with fresh thyme, if desired, and serve immediately.
Fresh thyme