Grilled top sirloin fillet is a highly flavorful, rich cut of meat. While it's not as tender as filet mignon, New York strip or porterhouse, the meat has a more intense flavor because it has a little less fat. For best results, cook top sirloin fillet to the rare or medium-rare point to keep the meat from drying out and becoming chewy.
Remove the top sirloin fillet from the refrigerator 60 minutes before you want to cook it to warm up to room temperature. Cover the meat with plastic wrap or aluminum foil.
Preheat a gas grill to the maximum temperature or preheat a charcoal grill for 30 minutes. Coat the surface of the grill liberally with corn oil.
Pat the top sirloin fillet dry with paper towels to remove any excess moisture.
Brush the top sirloin fillet with an even mixture of corn oil and vegetable oil to just coat the steak. Season the steak all over with freshly ground black pepper to taste.
Place the top sirloin fillet steak on the grill over the hottest part of the grill. Close the top and cook the steak for 2 minutes for rare meat, 3 minutes for medium rare and 4 to 5 minutes for medium.
Flip the top sirloin fillet over using a spatula and cook the steak for the same amount of time as the first side.
Remove the top sirloin fillet from heat and allow it rest on a serving plate for 5 minutes. Season the top sirloin fillet to taste with coarse ground kosher salt and serve it immediately while hot.