This recipe is based on wonderful fajitas served at a small authentic Tex-Mex restaurant near where I used to live. I have used this with both chicken and steak, flank steak or skirt steak, and it works great. I also mix a batch of the dry spices together and use a tablespoon or so when I make fajitas. The red onions, while not traditional, add a nice color to the fajitaas, but sweet yellow onions are more traditional. Note that the preparation time listed includes time to marinate.