Heat the oil in a large pot over medium heat. Add the garlic and saute for no more than 45 seconds (do not brown). Add the chicken broth and red pepper flakes.
Increase the heat to high and bring to a boil. Add the tortellini and cook for half the cooking time on the package. Add the tomatoes, reduce heat to medium-low and continue cooking until the tortellini is tender. Stir in the spinach and cook until it wilts (about a minute). Season if necessary with salt and pepper.
The flavors of this soup are good immediately - something I don't usually find with soups.