Warm butter in a skillet over medium heat. Sauté onion and bell pepper for about 5 minutes until soft.
Add the ground beef and taco seasoning to the skillet. Break the meat apart with a spatula as needed. Cook while occasionally stirring, about 5 minutes to lightly brown the meat.
Mix tomatoes into the meat. Bring the liquid to a simmer. Continue cooking everything for another minute or two.
Reduce the heat to low. Sprinkle cheese evenly over the meat. Cover the skillet with a lid and continue warming until the cheese melts completely. Remove from heat and garnish with cilantro. Serve warm with optional Cauliflower Rice.
