Separate the leaves of 4 little gem lettuce so that you have 20 of similar size. Wash and chill. Finely dice the flesh of 1 large, or 2 small, ripe avocados.
Mix with 1 tbsp lemon juice, 2 tbsp diced red onion, 2 tbsp diced yellow pepper, 2 tbsp chopped basil and 1 tsp extra-virgin olive oil. Season, mix and serve in the lettuce leaves topped with a halved cherry tomato.