Cooking with cast iron is not only incredibly easy, but super healthy, since the cast iron actually puts bits of iron into your diet. Unlike, say, cooking with lead, this is a good thing.
I like to make an omelet over the weekend with all the leftovers in our fridge. This weekend, it was a yellow squash/baby broccoli/red onion/tomato/bread/4 cheese mix omelet. Yum. The chickens donate their eggs in exchange for all the peels and odds and ends, so everyone's happy.
The first step is to just throw your veggies into the hot pan, with a little veggie oil. I like to soften the onions, squash or hard veggies like potatoes by cooking them first. If you're using up old bread, just crumble it up and watch for it to go brown and dry like a vegetable. The tomatoes can go last, when you're ready for the next step.
Next, your pour the eggs into that same pan - pre-mixed or not, your call. If it's looking a bit dry, you can spray it down with olive oil just before, but the pan should be good and oiled up at this point. Turn off the heat and find a tight-fitting lid. Quickly, now!
Last, sprinkle the top with cheese. This adds flavor, and richness so don't be skimpy! If you don't have some good, salty cheese like Parmesan then make sure and sprinkle on some salt as well. Pop the lid on and let the whole omelet cook with the remaining heat for about 5 minutes. Serve hot and goo-y with toast, if you like.