Cook the pasta until al dente, then set aside 2 cups of pasta water. Strain and rinse the noodles.
In the Dutch oven, add 2 tablespoons of pasta water and wilt the spinach over medium heat. Strain any excess water and transfer spinach to a mixing bowl.
Prepare the meatballs by combining 3 tablespoons of olive oil, egg, garlic, breadcrumbs, Italian seasoning, salt, and parsley with the spinach. Shape into balls.
Brown the meatballs in the Dutch oven with remaining olive oil, then remove from the pot.
Deglaze the pot with white wine, then sauté onion, garlic, and green pepper.
Add tomato paste and starchy pasta water, then return meatballs to the pot. Simmer until sauce thickens.
Toss cooked pasta with sauce and meatballs until heated through, then serve and enjoy!