Sift flour, salt, cinnamon and baking soda togather. Cream butter, brown sugar, sugar, peanut butter, egg and vanilla in mixer bowl until light and fluffy. Add sifted dry ingredients. Beat at low speed until moistened. Beat for 1 minute longer. Shape by 2tsp. into balls. Place on greased cookie sheet. Flatten with fork dipped in flour.
Bake at 350 degrees F. for 10 minutes or until brown. Remove to wire rack to cool.