Combine together butter, sugar, salt and baking powder. Mix in sour cream until you get once consistency.
In small portions add flour to the mixture until you get elastic dough.
Split dough into two balls, one a little larger than the other one.
Roll out larger piece for the bottom of the pie. Place dough in round cake pan, lifting up dough against the side so the pan.
Cut plums in halves, place them facing down inside the pie, cover all bottom very tight and sprinkle with sugar.
Roll out second piece of dough, cover the pie and with fingers pinch together the sides.
Bake at 400F for about 25 minutes or until golden brown on the outside.