Combine the beef, jerk seasoning, soy sauce and onion powder in a large bowl. Form the meat into 2-ounce patties.Heat a cast iron skillet or griddle over medium-high heat for 2 to 3 minutes. Place the hamburger patties in the pan. For medium-rare burgers, cook the patties for 4 minutes on each side. For medium burgers, cook the patties for 5 minutes on each side. Flip the burgers only once during cooking. Serve with dinner rolls, tomatoes, lettuce and red onions if desired.