1. Place the salmon fillet in a deep, oven-proof dish with the skin side down. Remove any bones. Dry the salmon fillet with kitchen paper.
2. Wash the beetroot and grate roughly. You do not need to peel it first. This can be a messy job so we recommend doing it over the sink.
3. Mix the grated beetroot with the sea salt, sugar, grated lemon and orange zest, chopped dill and a dash of Aquavit. The Aquavit is optional.
4. Spread the beetroot mix over the salmon and massage it in to the flesh. Cover the salmon with clingfilm. It helps to place something heavy, perhaps a full carton of milk, on top of the salmon while it is curing. Put the salmon in the fridge and leave for minimum 48 hours, or even longer.
5. After minimum 48 hours, remove the dish from the fridge and carefully remove the beetroot mix. You can also rinse the salmon. Dry carefully afterwards. The salmon has now been cured and can be thinly sliced.
6. Make the horseradish soured cream by mixing soured cream, grated horseradish, salt and pepper. Serve thin slices of beetroot-cured salmon on good flatbread with the horseradish soured cream and dill.