Marinate the Beef:
In a bowl, combine steak with garlic, lime juice, vinegar, oregano, adobo seasoning, and cumin. Toss well and let marinate for at least 30 minutes (or up to overnight in the fridge).
Cook the Onions:
In a large skillet, heat 1 tablespoon olive oil over medium heat. Add sliced onions and cook for 8–10 minutes until soft and caramelized. Remove from skillet and set aside.
Sear the Steak:
In the same skillet, add more oil if needed and increase heat to medium-high. Sear the marinated steak slices for 2–3 minutes per side until browned.
Deglaze and Simmer:
Return onions to the pan. Add beef broth and optional Worcestershire. Stir and bring to a simmer. Cover and cook on low for 8–10 minutes to tenderize the beef and blend flavors.
Serve:
Serve hot over white rice with a side of beans, tostones, or fried plantains. Garnish with fresh herbs if desired.