Your mom probably braised it. That’s how my mother in law made liver and onions and it was the most tender liver I’ve ever had. She dregged it if flour, browned it quickly on both sides, including the onion, then added water to cover and put a lid on it and braised it slowly for maybe a half hour. It made the best gravy, too.
That sounds a lot like it! We used to ask for it. :) We all had our favorite dinners and she would make them for our birthdays, along with the desert or cake of our choice.
Thanks! I never figured out the gravy part.