In a mixing bowl cream butter, gradually beat in sugar until light and fluffy about 7 minutes. Add eggs one at a time, beating well after each addition, stir in vanilla and orange zest..combine flour and baking powder, add to creamed mixture alternately with sour cream. beat on low speed just until blended. Fold in cranberries.
Pour into a greased and floured 10 inch tube pan and bake at 359F for 65 to 70 minutes or until a wooden toothpick inserted in center comes out clean. remove and cool in pan on wire rack for 10 minutes and remove from pan and cool on wire rack.
In small saucepan add sugar and flour stir in cream and butter and bring to a boil and cook for 3 minutes stirring constantly,remove from heat and stir in vanilla. serve warm over cake...pour sauce into a container and warm sauce in micro when serving later. This recipe yields about 1-1/2 cups of sauce.