Heat oil in a large pot or deep fryer with a thermometer to 350 degrees F. Cut corn tortillas into sixths. Fry chips in batches until they are golden brown and no longer bubbling, about 3-4 minutes per batch. Remove chips with a slotted spoon and transfer to a bowl lined with some paper towels. Season while warm with kosher salt.
For carne Asada:
Preheat oven to 350 degrees F. Mix together kosher salt, pepper, chili powder, paprika, and garlic powder in a small bowl. Drizzle flank steak with olive oil and season well with the spice mix. You can use it liberally to cover the steak, but you may not need all of it.
Heat a cast iron skillet over medium-high heat. Once hot, add flank steak and sear for 4 minutes per side. Then transfer to oven and roast for 5-6 minutes until the steak reaches 135 degrees F. in the thickest part. It’s okay if it’s undercooked slightly since it will bake again on the nachos.
Let steak rest for 10 minutes and then chop into small chunks.
NOTE: You can also grill the skirt steak or flank steak if you have your grill up and running.
To Make Nachos:
Heat oven to 400 degrees F. Spread chips out in an even layer on a baking sheet. Top chips generously with the carne asada, beans, red onions, cheese, and salsa. The ingredients should be enough to feed four so if you are just making it for two, you might have some leftover.
Sprinkle nachos with grated Monterey jack cheese and crumbled cotija cheese. Bake the nachos until the cheese is just melted, 4-5 minutes. Keep a close eye on it so the cheese doesn’t overbake and become hard.
Remove nachos and serve with any and all toppings of your choice!