Cut the skin and pith away from the grapefruit and separate the segments. Dice the tomato, roughly chop the avocado, and halve and finely slice the onion.
Pour off any excess juice and put the grapefruit segments tomatoes, avocado and red onion into a serving bowl, season well with salt and freshly ground black pepper and cover with the lobster meat. Squeeze the lime over the salad. Drizzle generously with olive oil and gently toss everything together.