Roast beef & caramelised onion roll

Heat 1 tsp olive oil in a frying pan over medium heat. Cook ½ red onion (sliced) for 10-15 minutes or until caramelised. Spread 1 (50g) wholemeal bread roll (halved) with 1 tbs mashed avocado. Top with 2 lettuce leaves, ½ tomato (thinly sliced), 50g deli-sliced rare roast beef and caramelised onion. Serve.