Dissolve yeast and sugar in warm water in a large bowl; add egg and sour cream, mixing well. Combine flour, salt and baking soda; add to yeast mixture, mixing well.Turn out dough onto a floured surface; roll to a 20 x 8” rectangle. Spread lemon blossom filling lengthwise down center of rectangle. Fold long sides to center, slightly overlapping edges; cut into 4x1” strips. Twist each strip oven, and place on greased baking sheet. Bake at 375º for 12-15 minutes. Frost with lemon blossom frosting while warm.
Lemon Blossom Filling: Combine all ingredients; stir until smooth.