Place all the burger ingredients in a mixing bowl and stir to combine.

Preheat the grill to hot. Cook the burgers under the grill for 15 minutes or until cooked through, turning once.

Top each burger with a slice of cheese towards the end of the cooking time.

Before serving, mix together the mayonnaise and lettuce. Cut the Ciabatta rolls in half and toast under the grill on both sides.

Top the bottom halves of the Ciabatta rolls with the lettuce and mayonnaise, followed by a slice of tomato.

Arrange the burger and cheese on top of the Ciabatta, followed by a slice of red onion. Top each burger with the other halves of the Ciabatta rolls and serve.