You Should Never Make Scrambled Eggs In A Cast Iron Skillet. Here's Why
Everyone has their own opinion about how to make scrambled eggs, the most classic of breakfast fare. Sometimes, these opinions can be quite strongly held. Whether or not you should add dairy to your scramble is a subject of great debate, as is what type of pan you should use. In fact, some cooks don't use a pan at all. Celebrity chef Gordon Ramsay, for example, uses a pot to prepare his scrambled eggs. Ramsay also warns against seasoning the mixture too early because the addition of salt at the beginning of the scramble can cause the eggs to break down and for the mixture to become watery. Again, this has been the subject of great debate, as well.
If you're really in a rush to get breakfast on the table, or have a serious aversion to doing dishes, there are even recipes that suggest a more unorthodox approach — scrambling eggs in the microwave (via The Incredible Egg). But never, ever scramble your eggs in a cast iron skillet.
Why cast iron poses a problem
Regardless of how much butter, oil, or cooking spray you add to the bottom of a cast iron skillet to try and prevent the stickiness, the eggs will adhere to the pan like glue, and you'll be left with a large portion of your scramble stuck completely to the skillet. Obsessively scraping the pan with a spatula won't help either, because the eggs aren't stuck so much as they are trapped.
The reason that eggs stick so intensely to cast iron is because cast iron pans aren't smooth (via Food Crumbles). If you run your fingers along the pan, you'll feel the friction and even if you look closely, you can see some of the crevices that are on the surface. Eggs get stuck in these crevices which is why we perceive them as them "sticking" to the pan.
Moreover, as Epicurious points out, cast iron takes on the the flavors of what you cook. Last night's fish taste in your scramble? Um, no thank you! The site also notes that a new cast iron skillet doesn't pair well with sticky foods like scrambled eggs; once yours is well-worn in — the surface becomes smoother with more use — it might be okay to try it out with a scramble. That being said, using a skillet with a non-stick surface is a much easier alternative.