Boil pasta. Reserve 1/2 cup pasta water for later.
Heat olive oil over medium heat in a large skillet.
Add onion and sauté until almost soft.
Add garlic and sauté another minute.
Add diced tomatoes, oregano, basil, red pepper flakes, salt and pepper to taste. Stir and cook a bit more.
Add meat and heat through.
Reduce heat to low.
Add something creamy and a bit of pasta water to the skillet.
Add parmesan and stir until melted.
Remove spinach stems and stir into skillet until wilted.
Add pasta to the skillet, stir and serve.