Saute the onions in a large pan or skillet until the onions are soft (about 2 min)
Add the seitan, making sure that the liquid it is packed in is drained first.
Add the BBQ sauce mix. Reduce the heat and let simmer about 5 - 7 min, stirring occasionally. Make sure the BBQ Sauce covers the seitan. You want to have lenough sauce so that the seitan can soak it up.
After the seitan is tender and well marinated with the sauce, turn up the heat to "high" and quickly stir-fry the seitan. This will sear the sauce onto each piece and give it a more crispy texture and an authentic BBQ look.
That's it! You can put it on a sandwich (see photo above) or just have it as a side dish, with brown rice, on top of a salad, etc. The possibilities are endless!