Prepare the dough. Place the shredded cheese, flour, and egg white into a mixing bowl and season, mix together by hand to form firm dough. You may use a food processor to make lighter work of it. Place in the refrigerator for at least an hour to firm.
Separate into 20g balls placing a cube of Gouda into each ball. Roll in flour and deep fry for 4-5 minutes. For the relish, preheat the oven to 200°C.
Have ready a large roasting tin or dish. Pierce the top of the tomatoes with the point of a knife, plunge them one by one into boiling water for 20 seconds, then into cold water, slip off the skins and coarsely chop the flesh, discarding the cores. Combine the chopped tomatoes with all the remaining ingredients in the roasting dish, and place in the oven, uncovered, for 1 hour, stirring towards the end, until reduced considerably. Serve with the cheeseballs.