Cream butter and sugar.
Add eggs.
Sift flour with baking powder, soda and salt.
Add to creamed mixture.
Stir in sour cream and vanilla.
Grease tube pan.
Put 1/3 of the streusel on the bottom, then half the dough, then another 1/3 of streusel, then the remainder dough and end with streusel.
Bake at 350° for 55 to 60 minutes.