Slice beef into thin strips about 2 to 3 inches in length and ½ inch in width. The inner thickness of the strips should be between 1/8 to a ¼ inch. You can always ask your butcher to slice them for you.
Place the juice of 3 limes, salt, pepper, chili powder, cumin powder, garlic, and chopped cilantro into a 1-gallon resealable plastic bag, and mix well.
Add the beef into the seasoning and mix to coat evenly.
Seal the plastic bag making sure to remove most air out of the bag. This will allow the flavors to penetrate more quickly into the beef, and it will also allow it to get tenderized quicker. Place the bag in the fridge and allow the beef to marinate for 2 to 4 hours or overnight.
Grill the marinated beef either in a cast iron skillet, or on a flat top grill over high heat for 3 to 5 minutes.
At the last minute of grilling the beef, add 2 tablespoons butter and a squeeze of lime. Remove from heat, and serve.
You can serve over taco shells along with some guacamole, or salsa verde. Garnish with some freshly chopped cilantro. Enjoy!
