1. Cut the avocado in half and remove the large pit. Carefully collect the flesh and transfer it to the bowl of a blender. Wash, dry, and finely chop the cilantro. Cut the flesh of half a tomato into small cubes.
2. Add the chopped chives, oat bran, lemon juice, and low-fat yogurt to the blender bowl, on top of the avocado flesh. Season with salt and pepper, then blend until you obtain a smooth mixture.
3. Immediately transfer the mixture into small glasses and decorate the top of each preparation with a few tomato cubes. Serve chilled.