For a nicer presentation, trim the salmon by slicing off the flat side. Freeze the small piece to use in another dish later. Place the salmon flesh side up on a large tray with sides or a container. Try to find something that just fits the salmon snuggly.
Roughly chop the beetroot into cubes and pulse a few times using a food processor, then blitz on high for 20 seconds or until it's finely chopped. Use a spice grinder or mortar and pestle to grind the coriander seeds and peppercorns.
In a large bowl, mix the beetroot with the gin, orange zest, coriander seeds, peppercorns, sugar and salt. The beetroot will break down, causing the mixture to look wet.
Place all the beetroot mixture, including the liquid over the flesh side of the salmon. Carefully, turn the salmon over with the skin facing up. Cover the salmon with cling/plastic wrap. Find a flat object that's heavy to place over the salmon to press it down. I used a wooden cheese board. Place the salmon in the fridge and leave it to cure for 2 or 3 days. The longer the better!
Remove the beetroot mixture from the salmon, then rinse it under cold water until the water runs clear. Pat both sides of the salmon dry with paper towels, then place it on a large plate and cover loosely with cling wrap. Chill in the fridge for another 24 hours for the flavours to develop further.
Finely slice the salmon and serve with rye bread and mustard dill cream. For the mustard dill cream: Combine all the ingredients in a bowl and mix well. Have a taste and add more salt or pepper to your liking if needed.