Trim steak and cut into serving-size pieces.
Pound with a meat mallet or the edge of a saucer to tenderize.
Combine flour, salt and pepper.
Dredge each piece of meat in flour mixture.
Use the mallet or plate edge to pound the flour mixture into the meat.
Heat oil in a large skillet over high heat.
Brown each piece of steak in the hot oil, setting aside when browned.
Add more oil if necessary.
When all meat has been browned, add sliced onions to the pan, separating as you add them.
Cook only until soft and remove from skillet.
Lower heat to medium and return meat pieces layered with onions to skillet.
Cook over medium heat until steak is tender and gravy has thickened, about 30-45 minutes.
If necessary, remove lid for last 15 minutes to let gravy cook down.
Can add flour (mixed with a bit of the gravy) to pan if necessary for thickening.