Cook the buckwheat in boiling water for approx. 3 mins. Remove the pan from the heat, cover and allow to absorb for approx. 15 mins.
Heat the oil in a non-stick frying pan. Stir fry the courgette for approx. 3 mins. Combine the lemon juice, oil and basil in a bowl, season. Add the tomatoes, radish, courgette and buckwheat to the dressing, mix.