Step 1

In a small bowl, stir together the cumin, ¼ teaspoon of the oregano and 1 teaspoon each salt and pepper. Using a sharp knife, score shallow cuts into the steak, perpendicular to the grain and spaced ½ inch apart. Now crosshatch at a 45-degree angle to the first cuts. Flip the steak and crosshatch the second side. Rub the cumin mixture into the cuts on both sides, then cut the steak into 2 or 3 pieces with the grain. In a 12-inch skillet over medium-high, heat the oil until barely smoking. Add the steak and cook, flipping once, until well browned and the center reaches 125°F (for medium-rare), 6 to 8 minutes. Transfer to a plate and tent with foil.

Step 2

In the same skillet over medium, melt the butter. Add the onion, tomato, garlic, remaining ½ teaspoon oregano and ½ teaspoon salt; cook, stirring, until the onion is wilted, 6 to 8 minutes. Add the lime juice and accumulated steak juices; cook, stirring, until slightly reduced, about 1 minute. Off heat, stir in the parsley. Taste and season with salt and pepper. Transfer the onion mixture to a platter. Thinly slice the steak against the grain and place on the platter. Serve with lime wedges.