That’s a beef tenderloin. The very best way is to use string and tie it up and curl the tail in to keep the thickness even. Season the meat with kosher salt and pepper to taste. Set the barbecue up to the lowest temperature possible (250 degrees) and grill the meat low and slow. Use an internal meat thermometer and pull it at 120 degrees. When the meat is off the grill, turn the grill up to as hot as it goes and then put the meat back on and grill it for 45 seconds a side to put a little crust on it. BBQ aficionados call this the reverse sear and it produces unbelievable results.