Place everything in a large jug and blitz the dressing using a hand held blender. Alternatively place everything into a food processor and blend until the dressing is smooth and pale green in colour.
Place the chopped tomatoes and sliced onions into a shallow salad bowl,
Pour over half of the dressing and add a little more olive oil for flavour along with the basil leaves. Enjoy with bread!
Keep the other half of the dressing in the fridge to enjoy another day.