Wash tomatoes to remove dirt and add to slow cooker. Add salt and pepper (optional) to taste. Add 2 cups water and butter.
Cook on high for 2 hours.
If you can lift the slow cooker insert safely, drain the potatoes, otherwise use a slotted spoon to remove the potatoes from the crock pot. Add dill and a small amount of butter if desired, stir well to combine and serve.