Begin by pickling the onions 1 hour before you want to serve the salad. Take the red onion and half it from root to tip, remove the skin and slice it thinly across the half moon and put it in a bowl. In a bowl mix the white wine vinegar and castor sugar together and ensure the sugar is dissolved. Pour the vinegar mix over the sliced red onion.
Cut the watermelon into 4cm chunks and arrange over a large plate or platter. Drain the red onion onto kitchen towel, and scatter over the chunks of watermelon.
Sprinkle pomegranate seeds and the sliced radish over the watermelon.
Take the herbs and scatter evenly over the whole dish.
Crumble the feta over the top.
Dress with a drizzle with olive oil and pomegranate molasses, and season with pepper.
Serve and enjoy.