Cook the lentils according to the package instructions in two and a half times the amount of water with about 1 teaspoon of vegetable stock until they are firm to the bite. This takes about 20 minutes.
In the meantime, cut the peeled apples, feta, paprika, onions and possibly cucumber into small cubes. Put everything with the cooked lentils in a salad bowl.
For the dressing, mix rapeseed oil, balsamic vinegar, mustard, and salt and pepper and pour over the salad.