Heat oven to 350F/ 175C.
Heat a 10 inch cast-iron skillet to medium heat. Add 1 Tbsp vegetable oil. When the pan is hot, add onion, red bell pepper, cumin, and salt. Saute until the vegetables are softened and slightly browned, about 5 minutes.
Add ground beef/sausage and gochujang. Break up meat chunks with a wooden spoon until cooked through and brown, about 5-8 minutes.
Remove from heat. Add cheese. Gently mix with a fork until well combined.
Transfer to the oven and bake for 5-7 minutes. The goal is for the cheese to gently melt. Watch carefully so that the cheese does not overcook and harden too much.
Remove from oven. Add kimchi to the middle in a small mound. Garnish with cilantro, green onion, avocado, red chili pepper (or jalapeno), and/or sour cream.Serve immediately with plenty of tortilla chips and lime wedges.