PUY LENTIL SPINACH AND TOMATO SALAD

1 small red onion, thinly sliced • 1 tbsp white wine vinegar • 250g pouch Merchant Gourmet Puy Lentils • 100g radishes, thinly sliced • 115g pack baby spinach • 1 gherkin, finely diced • 300g No.1 Jack Hawkins Tomatoes, halved and cut into thick slices • 20g pack fresh dill, chopped roughly • For the dressing • 1 lemon, juice • 2 tbsp olive oil • 1 tsp Dijon mustard • ½ tsp clear honey