Dilly Onion Braid

Let sour cream stand at room temperature for 1 hour. In a mixing bowl, dissolve yeast in warm water. Add the sour cream, egg, butter, sugar, salt and 1 cup flour. Beat on medium speed for 2 minutes. Add the onion, dill seed and dill weed; mix well. Stir in enough remaining flour to form a soft dough. Turn onto a floured surface; knead until smooth and elastic, about 6-8 minutes. Place in a greased bowl, turning once to grease top. Cover and let rise in a warm place until doubled, about 1-1/2 hours. Punch dough down. Turn onto a lightly floured surface; divide into thirds. Cover and let rest for 10 minutes. Shape each into an 18-in. rope. Place ropes on a greased baking sheet and braid; pinch seams to seal and tuck ends under. Cover and let rise in a warm place until doubled, about 30 minutes. Beat egg yolk and cold water; brush over braid. Bake at 350 degrees F for 30-40 minutes or until golden brown. Remove from pan to a wire rack to cool. ');