Preheat a large, oven-safe skillet over medium heat and add olive oil.
Add onion and cook 3–4 minutes until soft. Stir in garlic and cook 30 seconds.
Pour in the enchilada sauce and broth. Bring to a simmer. Let the sauce simmer uncovered for about 10–12 minutes to slightly thicken and develop flavor. Add salt and pepper to taste.
Stir in the tortellini, nestling them into the sauce. Spoon sauce over the tortellini if needed. Cover and cook 3 minutes, just until the tortellini are heated through and tender. Sprinkle cheese over the top, cover, and cook 2–3 minutes more until melted.