Dab the cured pork loin dry and place it on the fat pan of the oven. Peel the onion, cut it into pieces and spread around the Kasseler. Roast in the preheated oven (electric cooker: 200 °C/circulating air: 175 °C/gas: level 3) for about 1 hour.
After approx. 15 minutes, add 1/4-1/2 l water. Remove the roast and let it cool down for about 10 minutes.
Unroll the pizza dough on a lightly floured work surface, lay them next to each other with an overlap of approx. 5 cm so that a dough sheet of approx. 45 x 37 cm is created (remove paper). Spread with 5 tbsp. Ajvar, leaving a free edge all around.
Place the cured pork loin on the dough and beat it with it. Press the edges together. Place the cured pork on a baking tray lined with baking paper with the seam side down.
Wash the rosemary, pluck the needles and chop. Drizzle the roast with oil and sprinkle with rosemary. Bake in the preheated oven (electric cooker: 200 °C/circulating air: 175 °C/gas: level 3) for 25-30 minutes.
Stir together the sour cream and 3 tablespoons of ajvar. Season to taste with salt and pepper. Remove roast from the oven. Add Ajvar sour cream.