1. Place steaks inside a deep baking dish. Add and distribute onion rings on the steaks.
2. Mix orange juice, lime juice, beer, soy sauce, olive oil and pepper in a medium bowl.
3. Pour orange juice marinade over the steaks. Cover the baking dish with steaks and marinade, then refrigerate for an hour.
4. Fire up your grill and lightly oil grates to avoid meat from sticking.
5. Remove steaks from marinade and pat dry with absorbent paper towels. Place the steaks on the grill for 8-10 minutes per side.
6. Remove steaks from grill and place on a cutting board. Slice meat into portions and serve on warm corn tortillas topped with guacamole, salsa, lime, and onions.