Wash beef slices with cold running water. Pat dry with paper towel. Season beef slices with salt and ground black pepper.
In a small bowl, mix marinade – soy sauce, worcestershire sauce and fresh lemon juice.
Transfer beef slices into an airtight container. Pour marinade over seasoned beef slices. Top with red onion rings. Seal container. Refrigerate and allow beef slices to marinate overnight.
In a large skillet, sauté white onions and red onions (from the marinated beef) until translucent. Set aside.
In the same skillet over low heat, pan fry beef slices in batches. Slightly brown beef for about 2 minutes each side. Reserve marinade.
In a bowl, mix 3 tbsp. soy sauce, 1 tbsp. worcestershire sauce, 1 tbsp. lemon juice and brown sweetener (if using). Stir in reserved marinade.
In a pot of the slow cooker, lay some sautéed onion rings, top with beef slices. Repeat layers. Reserve a few pieces of onions for garnishing. Pour soy sauce and lemon mixture. Add beef broth. Slow cook for 4 hours in High heat or until beef is fork tender.
The dish is tastier as the meat incorporates longer with the sauce after being cooked. It’s even tastier a day after cooking, just reheat when needed.Butcher thinly sliced the beef sirloin with a meat slicer for an even thin cut.The beef was marinated for 24 hours in this recipe. You can opt for 1 to 2 hours of marinating but may need to adjust the soy sauce mixture and marinade to add more flavor.I used sirloin because it is the most tender cut of meat. The fresher, the better with this recipe. Other cuts of beef that will taste amazing with it are beef tenderloin or top round.