Cut the fish into 1 cm cubes. Place in a salad bowl. Add lemon juice, mix, cover and refrigerate for one hour. This will allow the fish to "cook" in its marinade.
In another bowl, prepare the other ingredients. Peel and dice the mango, then pour into the bowl.
Peel the garlic and onion. Finely chop the onion and dice the garlic. Mix with mango.
Just before serving, mix the fish with the other ingredients. Add salt, a pinch of chili powder, combava zest and chopped coriander, then mix and serve.