Score the fish: Lay it flat on a chopping board. With one hand pressing down the fish to keep it from sliding, take a sharp knife with the other hand and hold it at a 45-degree angle. Slash the fish, twice or thrice depending on the size, on both sides. How deep depends on the thickness of the flesh. I like depth of my slashes to be midway between the skin and the rib (spine).
Mix together the salt, pepper, ginger, garlic and lemon zest. Rub all over the fish including the cavity.
Place the fish in a covered container and allow to marinate in the fridge for at least an hour.
Pour water into the steamer pan and start heating.
Take the fish out of the fridge.
Smear the bottom of a heat-proof plate with half a teaspoon of olive oil.
Place the fish on the oiled plate and drizzle the remaining half teaspoon of olive oil over it (If adding a bed of spinach which is optional, spread the squeezed spinach on the plate and sprinkle with salt and pepper. Lay the fish on top of the spinach.)
Steam the fish for 30 minutes.
Take the fish out of the steamer.
Drizzle with lemon juice and more olive oil.
Optionally, garnish with fried garlic, lemon sliced and cilantro before serving.