Combine flour, salt, baking soda, baking powder and cinnamon; add into creamed mixture. Mix well.
Pour into lightly greased jelly roll pan. Bake in preheated 350° oven for 20 minutes. Test with a toothpick.
Mix frosting ingredients and frost when completely cooled.
NOTE: Cakes with cream cheese frosting should be refrigerated. We like these bars without frosting also.