To prepare the fish, remove the guts and clean with cold water. Using a sharp knife scrape the scales off the fish. Once cleaned and scaled, cut diagonal slices through the body of the fish to the bone about 5 cm apart.
Place the fish in the oven dish, season liberally with salt and pepper.
Cut the lemon into slices and place on top of the fish.
Drizzle with olive oil.
Place the fish in the oven and bake for approx. 45mins. The cooking time will depend on the size of your fish. You will be able to tell when it has cooked by checking the colour of the liquid at the base of the cuts. Once the flesh is white and the juices are clear it is cooked.
To prepare the salsa, combine in a bowl, the cucumber, lime zest and juice, coriander, red onion, chilli and a pinch of salt. Mix and taste. Season as desired.