For the pizza buns, sift the flour into a bowl and make a well. Add the yeast. Sprinkle with a pinch of sugar. Cut the processed cheese into small cubes.
Add the salt and the processed cheese cubes to the side of the bowl. Pour 125 ml of lukewarm water in and around the well. Then mix with the dough hooks of a hand mixer until a smooth dough is formed.
Let the dough rise, covered with a cloth, in a warm place for about 1 hour, until it has almost doubled in volume.
Meanwhile, peel and finely chop the onion. Wash, clean and finely dice the zucchini. Cut the ham into fine strips.
Preheat the oven to 200 degrees. Roll out the dough on a floured work surface to a rectangle of 20 x 30 cm.
Spread the tomato ketchup on the dough, leaving a 1 cm border. Place the diced onion and zucchini with strips of ham evenly over the tomato ketchup.
Season with salt, pepper and thyme. Sprinkle the grated Gouda on top. Roll up the pizza dough from the long side and press the edge firmly. Cut into 12 slices with a knife.
Place with the cut side on a baking tray lined with baking paper. Let rise again for about 10 minutes and bake the pizza rolls on the middle rack for about 20 minutes.