Peel the onion and cut in half then into thin slices. Sprinkle over 1 tsp salt and stir well. Add to a colander or sieve and leave for 10 minutes. Rinse the onion well and pat dry with paper towels.
Add the onion to a bowl and, using your hands or a spoon, combine with all the other ingredients. I like to leave my salad to rest for 15 minutes.
