This is my version of the steak served on the north fork of Long Island in the Elbow Room. I have been making it for over 30 years. It's also great on Porterhouse or T-bones. It's a great crowd pleaser on Filets or London broil, sliced thin. It tastes fine on a buffet at room temperature.
Put the soy sauce, onions and garlic in blender or food processor. Blend one minute on liquefy.
Add the seasoned salt and gravy master. Blend 30 seconds on liquefy.
Pour the marinade into a large Ziploc bag. Rub the steak with brown sugar and add the steak, seal the bag.
Leave the steak at room temperature, turning occasionally for 24 hours, or up to 3 days refrigerated and 12 hours at room temperature. Filet doesn't need as long as London broil. the more tender the steak the shorter amount of time it needs. It is safe at 75 degrees or below for 24 hours
Remove steak, shake off excess liquid. Grill steak to desired doneness. DO NOT save the marinade to reuse, and DO NOT serve as a sauce, since it had raw beef in it.
The steak will be almost black on the outside, it is not burned. The marinade is very dark in color.
Let the steak rest, 5 to 10 minutes, tented with foil, before slicing.