In a small bowl, combine ingredients for taco seasoning and set aside.
Season ground beef with salt and pepper.
Place a large cast iron skillet over medium high heat and add 1 tablespoon of olive oil.
Next, add onion and bell peppers to skillet. Cook until onions are translucent and tender. Then add garlic and cook for an additional minute.
Add ground beef and sprinkle taco seasoning over beef and vegetables. Mix well.
Cook ground beef until brown. Then mix in tomato paste and diced tomatoes.
Sprinkle cheddar and monterey jack cheese over beef and vegetables. Then remove skillet from heat and cover to allow the cheese to melt.