Step 1

Heat a barbecue flat plate or large frying pan on medium-low. Cook the onion, turning occasionally, for 15 mins or until very tender. Sprinkle with sugar and vinegar. Cook, turning occasionally, for 5 mins or until the onion caramelises. Transfer to a bowl.

Step 2

Heat a barbecue grill or chargrill on medium-high. Cook burgers for 4-5 mins each side or until cooked through. Top the burgers with cheddar slices and cook, without turning, for 1 min or until cheddar melts. Transfer to a plate.

Step 3

Meanwhile, cook the bacon on the grill for 1 min each side or until crisp.

Step 4

To make the paprika mayo, combine the mayonnaise, sour cream, lemon juice and paprika in a small bowl. Season.

Step 5

Divide the bun bases among serving plates. Spread bases evenly with the mayonnaise mixture and top with the lettuce, burgers, tomato, bacon and caramelised onion. Top with bun tops and serve immediately.