Simmer the lentils in boiling water over a medium heat for approx. 20 mins., drain, season with salt, set aside.
Combine the lemon zest, lemon juice and oil in a bowl, season, mix in the chervil and radish greens. Add the radishes, carrots and reserved lentils, mix.
Heat the oil in a non-stick frying pan. Add the rhubarb, stir fry for approx. 2 mins. Add the yacon syrup, simmer for approx. 2 mins., mix into the salad with the resulting liquid. Heat the oil in the same pan. Fry the salmon for approx. 3 mins. on each side, serve on top of the salad.