Cut the leaves off the beetroots - leaving a short stub to stop them bleeding (beetroot juice stains easily). Give them a good scrub under the tap and pop into a saucepan to boil for 30 to 40 minutes.
When cooked, douse under the cold tap to cool and rub off the softened outer skin with your fingers.
Grate the beets finely into a bowl and add plenty of lemon zest and all of the juice of the lemon.
Add the sugar and salt and stir to mix thoroughly.
Pour it over the salmon fillets and ensure the mixture covers the flesh completely.
Cover with clingfilm or an alternative airtight cover and leave in the fridge for 8 hours or overnight.
The salmon will be much firmer, now it is cured.
Scrape off the mixture and slice the salmon to serve on fingers of ryebread with optional ricotta and dill spread.
It can either be sliced very finely in typical Gravlax style, or can be cut thicker, around 5-8mm thick, a style closer to Sushi.