Sour cream sugar cookies

I would guess that this is Aunt Jenn'ys sour cream cookie recipe as she was the one who always had them on hand and I have not found any other hand-written recipe -- yet I know my mother made her cookies from Aunt Jenny's recipe.

Cream until very light:
2 cups sugar
1 cup shortening
3 eggs
1 cup sour cream
1 teaspoon soda
1 teaspoon flavoring (Vanilla, lemon, or combination of both)
3 teaspoons baking powder
1 teaspoon salt
5 1/2 cups floor

Beat sugar and shortening until light, add eggs one at a time and beat well.
Dissolve soda in sour cream and add to first mixture.
Add flavoring and then baking powder and salt which has been mixed with flour (enough to make it easy to handle.)
Roll 1/4 inch thick and cut with three inch round cutter.
Sprinkle with a little sugar.
Bake at 350 until edges start to brown slightly.