4 pink grapefruit
250 g prawns, previously cooked
1 fully ripe avocado
2 tomatoes
1 yoghurt
juice of 1 lemon
2 tablespoons ketchup
salt

Cut the grapefruits crosswise at the top. Scoop and chop the flesh removing fibres. Peel the tomatoes and dice. Peel the avocado, crush and soak with some lemon juice. Peel the prawns. Make the sauce with the remainder lemon juice, yoghurt, 2 tablespoons ketchup and season to taste. Mix the prawns with the tomatoes, avocado and the grapefruit. Blend with the sauce and pour into the scooped grapefruit. Serve cold.