To the milk add, salt, pepper, cumin and coriander, whisk to mix. Add milk mixture to a small frypan; bring to a low simmer, add fish and simmer about 3 minutes, carefully turn the fish and simmer another 2 minutes, Turn the heat off leaving the fish in the milk.
Take 4 or 5 tablespoons of the poaching milk and add to a small pot; add corn, tomato,red onion, cumin, coriander and cayenne pepper; stir to mix; bring to simmer, simmer for 2 minutes.
Remove the fish from the milk to a serving plate. Spoon the relish over the fish in a neat line. Serve immediately.