One of the food blogs that I read is called Smitten Kitchen. It's gorgeous. I want to make everything she posts. But, when I saw her version of Huevos Rancheros, I just had to try it immediately.
You can follow the step-by-step instructions (with pictures!) at Smitten Kitchen, but it's an easy enough recipe for me to explain.
Heat a corn tortilla in a non-stick pan with a little oil. When it's brown, flip it over. Sprinkle some shredded cheese on the tortilla, then carefully crack an egg on top. When it's about half-way set, flip it over (again, be careful). When the egg is cooked, flip it back over onto a plate. Decorate with black beans, chopped tomatoes/onions/jalepenos (or use prepared salsa), avocado & sour cream.
This is really, really tasty and makes for a great weekend morning brunch or a light supper.