In a large pot, simmer the vinegar till it reduces to half and is really thick. You don’t want to boil this as it will stink up your whole house…trust me. You don’t want to skip this step, as reducing the vinegar brings out the natural sweetness.
Once the vinegar has cooled completely add the salt, pepper, and brown sugar and mix thoroughly, making sure the sugar is dissolved completely.
Slice very thin the cucumbers and tomatoes, I use a mandolin. But a very sharp knife will work also.
Place the vinegar mixture in a zip baggie, and add the vegetables zip and toss. Put the baggie into a bowl or some kind of container in case of leakage…..Place in the refrigerator for at least several hours. Toss the vegetables every ½ or so in the bag….
When it time to serve, drain the liquid reserving it for a later use.