Preheat oven to 350° F. and butter and flour two 8-inch round cake pans, knocking out excess flour.
In a bowl whisk together flour, baking powder, and cinnamon. In another bowl with an electric mixer beat together shortening and sugar until light and fluffy. Beat in milk and beat in eggs, 1 at a time, beating well after each addition. Add flour mixture and beat until smooth. Divide batter between pans, smoothing tops, and bake in middle of oven 30 minutes, or until a tester comes out clean. Cool layers in pans on a rack 10 minutes and invert onto rack to cool completely.
In a bowl with an electric mixer beat together cream cheese and butter until smooth. Gradually beat in confectioners' sugar until combined and beat in lemon zest and juice.
Assemble cake, spreading frosting between layers and on top and side.
