Run your fingers across the top of the salmon fillets, removing any bones you find.
In a large bowl, mix together the salt, muscovado sugar and granulated sugar until well combined.
Grind the dill seeds, coriander seeds and cracked black pepper to a powder in a pestle and mortar. Sprinkle the seed powder over the salt mixture, then stir in the lime zest, gin and chopped fresh dill until well combined.
Take a large piece of aluminium foil, large enough to wrap around both fillets of fish, and place one fillet of salmon, skin-side down, on top of it.
Cover the salmon fillet with all of the salt mixture, then place the remaining salmon fillet, skin-side up, on top of it. Wrap the fillets tightly in the foil, then pierce a few holes in it using a cocktail stick (this allows excess liquid to drain from the fish).
Place the fish onto a baking tray and place another baking tray on top. Weigh the top baking tray down with a couple of house bricks or weights from a set of kitchen scales. Chill in the fridge for 2-3 days, turning the packet of fish every 6-8 hours, where possible.
To serve, unwrap the salmon, scraping off any excess salt mixture. Slice the fillets very thinly on the diagonal using a sharp knife, and serve with a wedge of lemon, rye bread and a simple green salad.