Mix the flour, whole wheat flour, baking powder, grape sugar and salt. Whisk the egg with the yogurt. If you like, you can add a few more sunflower seeds to the batter. Mix the flour and yoghurt mixture with the dough hook. Knead the mixture on a floured work surface to form a smooth dough. Shape the dough into a round loaf and sprinkle with sunflower seeds if necessary. Place the loaf on a tray and bake at 180 ° C for about 40 minutes until golden brown.