Using a large sealable baggie, add cumin, chili powder, garlic salt, pepper, crushed red peppers. Seal and shake to combine then add lime juice, seal and shake to combine.
Add skirt steak to baggie, seal and place in fridge for 4+ hours or overnight, turning a couple times during marinating.
Heat a large cast iron skillet over medium high heat and add 2 tablespoons of oil to pan.
Once oil is hot, add onions and bell peppers. Cook until peppers are tender but still crispy. Place on a plate and set aside.
Add remaining oil in skillet, place steak into pan, discard liquid.
Cook on high for 5-6 minutes per side, for medium.
Remove steak from skillet and place on cutting board. Cut into ½" bite size pieces and add back to skillet along with onions and bell peppers.
Place tortillas chips on a large, oven safe, platter, top with cheese, add steak mixture on top of cheese, then add remaining cheese on top of meat.
Place in a 350° preheated oven just until the cheese has melted.
Carefully remove from oven and garnish with additional optional ingredients: refried beans, guacamole, charro beans, Pico de Gallo, sour cream, cilantro, green onions and sliced jalapenos.