1. Heat a large, heavy-bottom pot over medium-high heat. Add olive oil once hot, then add the Italian sausage. Cook the sausage until just starting to brown, about 5-7 minutes. Add the diced onions and 1/2 tsp. kosher salt, and sauté for 7-8 minutes, or until onions are translucent and soft. 
2. Add minced garlic and sauté about 30-60 seconds, stirring frequently. Add another 1/2 tsp. of kosher salt, the black pepper and Italian seasoning, and stir until distributed. 
3. Add the wine (if using) and diced tomatoes, and stir to release browned bits from the pan. 
4. Add the jarred marinara sauce and vegetable broth to the pot, and stir to combine. (Tip: Add some of the vegetable broth to the empty marinara jar, and shake to get all the sauce out of the jar.)
5. Bring to a boi, then add pasta and simmer for about 8 minutes (or the minimum length of time according to pasta package directions). Stir occasionally so that pasta doesn’t stick to the bottom.
6. Once pasta is al dente, add frozen spinach, and cook an additional 3-5 minutes until pasta is tender and spinach is wilted.
7. Serve immediately, ladled into bowls, and top with grated parmesan cheese. Store leftovers in an airtight container in the fridge 3-5 days.

Notes: 

• If omitting the wine, substitute with additional broth or water, and a splash of balsamic vinegar for flavor.
• Use any large jar of your favorite marinara sauce. I’ve tested this recipe with jars ranging from 24 to 32 ounces in volume.