Preparation: In a bowl, combine adobo sauce, olive oil, cumin, oregano, black pepper, and salt. Mix until well incorporated.
Marination: Place the sirloin steak in a zip-top bag or shallow dish. Pour the marinade over the steak, ensuring it's fully coated. Seal the bag or cover the dish, and refrigerate for at least 1 hour or up to overnight for deeper flavor.
Cooking: Preheat your grill or a cast-iron skillet over medium-high heat. Remove the steak from the marinade, letting excess drip off. Cook the steak on the preheated grill or in the large skillet for about 4-5 minutes per side for medium-rare, or until your desired level of doneness is reached.
Rest & Serve:Remove the steak from the heat and let it rest for 5 minutes. Slice against the grain and serve.