Cut steak across grain into 1/4-inch slices; cut slices into 1/2-inch-wide strips.
Cut strips into 3-inch-long pieces.
Combine steak pieces, 1/4 cup onions, sugar, soy sauce, garlic, and sesame oil.
Heat a 14-inch wok over high heat.
Add 1 tablespoon canola oil to wok, swirling to coat.
Add half of steak mixture to wok; stir-fry 2 minutes or until lightly browned. Spoon cooked steak mixture into a bowl. Repeat procedure with remaining 1 tablespoon canola oil and remaining steak mixture.
Sprinkle with remaining onions and sesame seeds. Spoon 1/4 cup rice, about 2 tablespoons steak mixture, and 1 tablespoon kimchi onto each lettuce leaf; roll up.