Place the corn or peas on a plate and pat dry using paper towel/s then place in a bowl with onions, cucumbers and celery (DO NOT add in the tomatoes you will add them in just before serving) toss to combine.
Mix all the dressing ingredients together until well combined.
Pour over the veggies; mix well to combine.
Season with black pepper and more salt if needed.
Cover and chill for a few hours to blend the flavors.