Thinly slice the steak against the grain of the meat for the most tender slices. If your knife skills are lacking, you can freeze the meat and then allow the meat to thaw overnight in the fridge. This will give you a firm, yet pliable piece of meat that is easy to slice very thin. Place all the meat into a medium sized mixing bowl, then combine it with soy sauce, lemon juice and black pepper. Use freshly cracked black pepper, if possible. Allow it to sit as you slice onions or refrigerate it overnight for the best flavor. Slice the yellow onion by removing the ends and the papery skin. Then cut it in half and then slice each half into thin julienne slices. Heat a large saute pan over medium high heat until the pan is hot. Add the avocado oil and swirl the pan to distribute the oil into an even layer. Add the meat along with the marinating juices.
Bring the mixture to a boil and then down to a simmer. Cover the saute pan with a lid (if you do not have a lid, you can use a baking sheet to cover it). Simmer the meat until tender. This will depend on the type of meat you choose to use and even your particular cut, this will take at least 30 minutes. Keep an eye on the pan and be sure to add more water to the pan if it starts to get dry. Once the meat is tender, remove it to a clean bowl.
Add 1 tbsp of avocado oil to the pan and then add the onion and minced garlic and saute them until lightly caramelized. Add the meat back in and give the dish a good stir. Taste adding more salt or black pepper.
Serve immediately with your favorite Keto side dish or cauliflower rice.