In a large pot (at least 5.5 quarts), add olive oil and chopped onion. Sauté over medium heat until slightly softened and aromatic.
Next, add the chopped chicken, Italian seasoning, garlic, red pepper flakes and salt and pepper to the pot with the onions. Sauté and stir until the chicken is almost cooked through –approximately 3 to 4 minutes.
Add chopped red bell peppers, jarred tomato marinara sauce, "2 cups" chicken broth (reserve ½ cup for later) and cook over medium-high heat for 5-8 minutes until bubbly. Cover and stir occasionally to prevent sticking.
Then add capers, kalamata olives and tortellini or tortelloni pasta and ½ cup extra chicken broth to the pot. Cover and cook according to the directions on your tortellini package. Stir occasionally to prevent sticking. Our pasta was cooked in 8 minutes. Adjust seasoning as needed. If your marinara sauce is too tart, add 1 teaspoon of sugar to balance the flavors.
Remove the lid from the pot and turn off the burner on the stove, add in fresh spinach and stir. Sauce will thicken upon sitting.
Garnish with parmesan cheese or enjoy plain with a drizzle of extra virgin (EVOO).