Heat the pan: Set a large skillet over medium heat.
Add olive oil or butter and let it warm until shimmering.
Sauté the aromatics: Add onion and bell pepper. Cook 3–4 minutes until softened. Stir in garlic and cook 30 seconds until fragrant.
Add the veggies and beans: Stir in corn and black beans.
Season with a pinch of salt and pepper. Cook 1–2 minutes to heat through.
Season it up: Sprinkle in chili powder, cumin, and smoked paprika. Stir to coat the veggies evenly.
Build the base: Pour in the diced tomatoes with their juices.
Stir well.
Choose your rice path: Using uncooked quick-cook rice: Add rice and 1 1/2 cups broth. Stir, bring to a gentle simmer, then cover and cook 10–12 minutes (or per package directions) until rice is tender and liquid is absorbed.
Using cooked rice: Add 1/2 cup broth and the cooked rice. Stir and simmer uncovered 3–5 minutes until warmed and slightly saucy.
Add a splash more broth if it looks dry.
Fold in the leftover beef: Stir in the cooked ground beef. Taste and adjust salt and pepper. Let it heat 2–3 minutes.
Melt the cheese: Sprinkle cheese over the top.
Cover for 1–2 minutes until melty and gooey.
Finish and serve: Top with cilantro or green onions. Add lime wedges, sour cream, or hot sauce if you like. Serve straight from the skillet.