To make the tomato and basil topping, place the tomatoes, red onion and oregano in a bowl. Add a small dash of oil, season with salt and pepper and stir. Allow to rest for a few minutes so all the ingredients marry together. Just before serving, tear the fresh basil leaves and stir them into the mix, then spoon the topping onto the toasted bread. You must eat this bruschetta right away after adding the topping or the tomato juices will soak the bread and ruin its crunchy qualities.