While I can understand what a steak omelette is, no, I have never seen this on a menu at Disney.
Most often, an omelette at Disney is made with meats that are going to have 'traditional' American options of bacon and/or sausage (maybe even chicken sausage).
Narcoossee's & CA Grill have steak-n-eggs at their Sunday brunch, and Kona has steak'n'eggs every day.
I find the buffet at Fresh to be outstanding. You can select your own filling for your omelette yourself, the omelette is made to order. This could certainly include the carved meats they offer (but I'm thinking these are pastramied-turkey and/or a big ham).
Hhhhmmmm......Steak omelette, I'm gonna' have to speak with a friend that owns a top-notch breakfast place near where I live.....