In large bowl, combine flour, baking soda, baking powder, salt and 1/4 cup of the buttermilk. Add egg yolks, sugar and vanilla; beat at medium speed until smooth. Add remaining 1/4 cup buttermilk and sour cream; mix well. In medium bowl, add cream of tarter to egg whites; beat until stiff. Fold egg whites into batter. Heat griddle; grease with butter. Spoon batter onto griddle to crepe thickness. Cook until light brown on both sides. Serve with powdered sugar or jelly if desired.