Aunt thirya's sugar cookies

1. In a large bowl with an electric mixer cream the butter with 2 cups of the sugar until the mixture is light and fluffy and beat in the eggs, the sour cream, and the vanilla.

2. Into the bowl sift together the flour, baking powder, the baking soda, and the salt and blend the mixture until it forms dough. Roll tablespoons of the dough into balls, arrange the balls of dough 3 inches apart on lightly greased baking sheets and flatten them with the bottom of a glass dipped in sugar until they are ¼ inch thick. Sprinkle the cookies with the additional sugar and bake them in batches in the middle of a preheated 375-degree oven for 10 minutes or until the edges are golden. Transfer the cookies to racks and let them cool.