Take melted butter and sugar in a large mixing bowl an stir. Add egg yolk, orange zest, orange juice, and baking soda. Gradually add the flour and knead the dough until the dough reaches a soft consistency. Take small parts ( about the size of walnut ) from the dough and give them the shape of small balls. Press an indentation into each ball with your finger. Dip ( just one side of the cookies ) them first into egg white and then coat with almonds. Place them on a greased baking tray. Preheat the oven 350 F. Bake the cookies for 15 to 20 minutes. When it is completly cool fill the indentations with orange jam.