Mix together the garlic powder, onion powder, meat tenderizer, and seasoning salt in a small bowl. Rub the seasoning blend into both sides of the steaks.
Arrange 1/4 of the sliced onions in the bottom of a 9x13 inch pan, lay steaks across the onions, top with more onions and pour 1/4 cup of lime juice and 1/4 of the bottle of beer over the top; repeat these layers until you run out of steaks, pouring all remaining lime juice and beer over the top. Cover and refrigerate for 30 to 40 minutes. Do not marinate the steaks for longer than an hour, because the acid from the lime juice in the marinade will begin to cook the meat.
Preheat an outdoor grill for medium-high heat and lightly oil grate. Place steaks on the grill and discard the marinade.
Grill the steaks to your desired degree of doneness, or about 2 minutes per side for well done. Remove from the grill and allow to rest for 5 minutes before slicing and serving with warm tortillas.