Mix baking soda with water. Add salt and buttermilk and mix everything together. Stir in the vinegar (something foams).
Put both types of flour in a bowl and pour in the liquid. At this point you can add grains as you like. At the moment I add flax seeds, sunflower seeds and pumpkin seeds (50g each).
Work the dough through well with the dough hook (no rest periods are necessary). Shape the dough into a loaf, place on a floured baking sheet, dust with flour and cut a few times.
Put the bread in the oven and bake at 180 ° C for about 45 minutes.