Preheat oven to 300 F. Beat 1 cup butter, 1/2 cup powdered sugar and vanilla until smooth. Mix flour and baking powder. Add into butter mixture. Stir to mix, then beat until well blended. Stir in pecans. Shape into balls (1-inch) and place on greased cookie sheet and 1-inch apart on buttered 12-by-15-inch baking sheet. Bake for 25 minutes. Put 1 1/2 cups powdered sugar on a plate and roll them in powdered sugar while warm. Roll them again in powdered sugar. Put them in airtight container.