Wash, clean, peel and slice the beetroot into thin slices. Quarter 1 sour apple (150 g, e.g. Elstar), remove seeds and cut into very fine slices. Mix apple slices with 1 tbsp. lemon juice.
Mix 1 tbsp lemon juice with 3 tbsp apple juice, salt, pepper and 1⁄2 tsp sugar. Stir in 4 tbsp. olive oil. Roast 3 tbsp. sunflower seeds in a pan without fat, season with 1 pinch of salt and 1 pinch of sugar.
Mix beetroot and apple slices in a bowl with the dressing. Sprinkle with 100 g crumbled feta, cut cress from 1⁄2 bed and sunflower seeds.