In a shallow dish, place the all-purpose flour, garlic powder, salt, and pepper. Mix well.
Dredge each liver slice in the seasoned flour, shaking off any excess.
In a large skillet, heat the vegetable oil and butter over medium-high heat.
Add the liver slices to the skillet and cook for 2-3 minutes on each side, or until they’re browned and cooked to your desired level of doneness. Liver is best when it’s still slightly pink in the center.
Remove the liver slices from the skillet and set them aside.
In the same skillet, add the thinly sliced onions and cook them over medium heat, stirring occasionally, until they’re caramelized and golden brown. This will take about 15-20 minutes.
Once the onions are caramelized, return the liver slices to the skillet, allowing them to reheat briefly.
Serve your Beef Liver and Onions hot, garnished with chopped fresh parsley if desired.