Peel the potato and quarter it lengthways. Mix the oil, a little salt, pepper and paprika into the potatoes. Spread the potatoes on a baking sheet.
Bake in a preheated oven (top / bottom heat 200 ° C, fan oven 175 ° C) for about 30 minutes until golden brown. Turn the potatoes halfway through cooking.
For the dip, roast sunflower seeds in a pan without fat, remove and let cool down.
Cut the radishes into fine sticks and the cucumber into cubes. Finely dice the onion. Mix the quark and buttermilk and season with salt and pepper. Mix in the onion, radishes, cucumber and sunflower seeds, except for something to sprinkle in. Cut off half of the cress and mix in as well.
Arrange the potatoes with the dip on plates and serve sprinkled with the remaining radishes, cucumber, sunflower seeds and cress.