In medium bowl, stir together beef, chili powder, salt, pepper and garlic powder. Divide into 6 portions and roll into balls.
Press a beef ball over each tortilla to form a thin patty, leaving a ½-inch border.
In large skillet set over high heat, heat 1 tbsp oil. Arrange 2 tortillas, with beef mixture facing down, in skillet. Cook for 2 to 4 minutes or until beef is browned and cooked through. Flip and cook for 1 minute. Transfer to a plate and cover to keep warm. Wipe skillet clean with paper towel. Repeat with remaining oil and remaining prepared tortillas.
Top each tortilla burger with lettuce, tomato, onion and Cheddar. Fold to eat like a taco.
Tip: Serve with drizzles of mustard and mayonnaise.