Rinse the fish, dab dry, chop or mince. Squeeze lime. Marinate the fish in the juice for about 15 minutes.
Peel the shallots and cut into fine strips. Wash coriander, shake dry, cut leaves roughly. Halve the avocado and stone it. Remove the flesh and dice. Mix everything with the fish.
Season with salt, pepper and 1 pinch of sugar.
Toast bread in hot oil in a (grill) pan until golden brown. Spread the fish mix over it.