Cook the beets: In a pot, boil the beet(s) until tender. To test, poke a knife through the middle—if it goes through easily, they’re done. Drain and let cool.
Cook the buckwheat: Rinse the buckwheat thoroughly. In a pot, bring 375 ml (1.58 cups) of water to a boil. Reduce the heat, add the buckwheat and juice from half the lime/lemon. Cover and let simmer on low until the water is fully absorbed (about 10 minutes). Remove the lid and let cool until lukewarm.
Prep the horseradish: Peel, wash, and finely grate the horseradish using a kitchen grater or a food processor with a fine grating attachment.
Prep the beets and celery: Peel the cooled beets and dice them into small cubes. Wash the celery and cut into small pieces.
Assemble the salad: In a bowl, gently mix the buckwheat with the celery, beets, and grated horseradish.
Finish and season: Stir in the rapeseed oil, rice syrup, and the remaining lime/lemon juice. Season with salt and pepper to taste.
Notes
*You can substitute rice syrup with another liquid sweetener like molasses, agave, or maple syrup. Since these are slightly sweeter, use just 1 tablespoon.