For a fast, low-calorie dinner, try this Tex-Mex classic. It uses top round steak, which is a very lean cut of beef, plus it packs plenty of fresh flavor. Other lean cuts of beef, like eye of round or top sirloin, will also work in this recipe.
In a shallow dish or bowl, combine steak, soy sauce, and 1/4 cup lime juice. Refrigerate 1 hour, turning steak occasionally. Meanwhile, in a small saucepan, heat 2 teaspoons oil over medium. Add garlic and cook until fragrant, 30 seconds. Remove from heat. Stir in 1 tablespoon lime juice. Set garlic oil aside.
Remove steak from marinade and blot dry with paper towels. Season with salt and pepper. In a cast-iron or heavy skillet, heat 1 teaspoon oil over medium-high. Cook steak until medium-rare, about 2 minutes per side. Transfer to a plate and loosely tent with foil.
Add peppers and onion; season with salt and pepper. Cook, stirring, until vegetables are crisp-tender, 4 to 6 minutes. Stir in reserved garlic oil. Thinly slice steak and serve with vegetables, tortillas, cheese, tomato, and cilantro.
To warm up corn tortillas, wrap in damp paper towels and microwave them for 1 minute, or toast them over a stovetop burner using tongs.