In a large bowl, cream butter and sugars until light and fluffy. Beat in egg and vanilla. Combine the flour, baking powder, salt and cinnamon; gradually add to creamed mixture. Fold in cranberries and walnuts.
Spread into a greased 9-in. square baking pan. Bake at 350° for 30-35 minutes or until a toothpick inserted in the center comes out clean. Cool on a wire rack. Cut into bars.