Heat a tortilla in a pan that has been coated with oil. When it turns golden brown, flip it over, and sprinkle some shredded cheese on the side that has browned.
When the cheese has melted a little, crack an egg over it. The secret here is to keep your heat at about medium so you don't burn the tortilla to bits. The egg will run, but that's OK. We aren't going for Martha Stewart perfection here. When the egg has set or started to turn white at the edges, flip the entire thing over. This gets messy, trust me, but it's OK. Just cook the egg for a few more minutes and then flip it onto a plate.