Put the vinegar in a small bowl. Rub the peel of the lime and squeeze out the juice. Add both to the vinegar. Stir in the olive oil and add the finely diced onion. Let it marinate while you prepare the rest of the salad.
Put the watermelon cubes in a large bowl. Wash the mint, pluck the leaves, cut into fine strips and add them to the melon. Cut the feta cheese into small cubes and add them as well. Finally, wash and clean the rocket and add to the salad.
Spread the dressing over it, mix well and serve immediately. Sprinkle any roasted pine nuts or sunflower seeds on top just before serving.
Tip: The watermelon salad tastes best when the melon is ripe (and sweet) but still firm. Cut it into approx. 1 cm cubes with an extra sharp knife so that it doesn`t get mushy.