Pat the sirloin dry with paper towels. Trim any excess fat and, if the steak is thicker than 1 inch, use a meat mallet to gently pound to an even thickness of about 3/4–1 inch. This helps even cooking and better marinade penetration.

Make the marinade

In a medium bowl combine olive oil, soy sauce, lime juice, brown sugar, minced garlic (finely chopped or pressed), grated fresh ginger, red chili flakes, hot sauce, ground cumin, smoked paprika, black pepper, and kosher salt. Whisk until sugar dissolves and the mixture is homogeneous.

Marinate

Place the steak in a shallow dish or zip-top bag. Pour the marinade over the steak, turning to coat both sides. Press out excess air if using a bag and seal. Refrigerate for at least 30 minutes and up to 4 hours. (Do not exceed 8 hours; the acids can change the texture.) Remove steak from fridge 20–30 minutes before cooking to come toward room temperature.

Preheat cooking surface

About 10 minutes before cooking, preheat a heavy skillet (cast iron recommended) over medium-high heat until very hot, or prepare a grill to medium-high. If using a skillet, add 1 tsp neutral oil to coat the surface right before adding the steak.

Sear the steak

Remove steak from marinade, letting excess drip off (reserve marinade). Place steak on the hot skillet or grill. Sear without moving for 3–4 minutes to form a crust. Flip and sear the other side for 3–4 minutes for medium-rare (internal temperature ~130–135°F / 54–57°C). Adjust time ±1–2 minutes for desired doneness.

Finish with butter and reserved marinade (optional)

If using a skillet, reduce heat to medium-low. Add 1 tablespoon of butter and 2 tablespoons of the reserved marinade to the pan (do not add raw marinade to a grill). Spoon the melted butter and pan juices over the steak (baste) for about 30–60 seconds to build flavor. If the reserved marinade was used, bring it to a boil in the pan for at least 1 minute to ensure safety before basting.

Rest

Transfer the steak to a cutting board and tent loosely with foil. Let rest for 5–10 minutes. Resting redistributes juices and finishes carryover cooking (steak will rise a few degrees).

Finishing & Garnish

Slice and serve: Slice the steak thinly against the grain for maximum tenderness. Arrange on a platter.

Garnish: Sprinkle chopped cilantro and optional sliced green onions over the sliced steak. Serve with lime wedges alongside so diners can squeeze fresh lime juice over the meat for brightness.

Serving suggestions: Serve Spicy Sirloin with rice, roasted vegetables, grilled tortillas, or a crisp salad.