Warm salad with lentils, pistachios, grapes and feta cheese

A lukewarm salad good for both lunch and dinner, all year ’round.
Should there be some leftovers, it’s perfect for a lunchbox for tomorrow at work! Save the salad separately from the feta cheese, so you can warm the salad slightly and then sprinkle over the feta cheese.
Cooking time: 30 minutes if you use dried green lentils. 20 minutes if you buy precooked lentils or precook them yourself.