Remove beef from packaging and place in a bowl with water and vinegar for up to 5 minutes.
Rinse and dry your beef.
Slice half of an onion into rings and set aside.
With the remaining onion, rough chop and add to bowl with the beef.
Chop 4-6 cloves of garlic, add to beef.
Add juice of 1 lemon, 4 tbsp of soy sauce, garlic powder, and black pepper to the beef.
Mix beef with marinade and let sit in fridge for at least one hour or overnight.
In a small bowl, make a cornstarch slurry using 1 tbsp of cornstarch and water. Set aside
In a large pan or wok, add a high temp oil like avocado or canola and fry the onion rings. Set Aside.
Add a little more oil to the same pan, and fry the beef. Leave the marinade aside.
Once the beef is all browned, set aside. Add 1-2 cups of water to your marinade.
Pour Marinade into the pan with the cornstarch slurry and let thicken.
Add beef back into thickened marinade and cook for 7-10 minutes till beef is tender and fully cooked. Add the sauteed onion rings.
Serve over white rice and enjoy :)