1. Preheat oven to 350°.
2. To prepare cake, weigh or lightly spoon cornmeal and flours into dry measuring cups; level with a knife. Combine cornmeal, flours, baking powder, and xanthan gum in a medium bowl; stir with a whisk. Place sugar and butter in a large bowl; beat with a mixer at medium speed until light and fluffy. Add eggs, 1 at a time, beating well after each addition. Beat in lemon rind. Add flour mixture and buttermilk alternately to sugar mixture, beginning and ending with flour mixture.
3. Pour batter into a 9-inch springform pan coated with cooking spray. Bake at 350° for 40 minutes or until a wooden pick inserted in center comes out clean. Cool 10 minutes in pan on a wire rack.
4. To prepare glaze, combine powdered sugar and lemon juice in a small saucepan. Bring to a boil over medium heat, stirring constantly; cook 1 minute or until sugar dissolves. Remove from heat.
5. Pierce entire surface of cake with a wooden pick. Slowly pour warm glaze over cake, letting it soak into cake. Sprinkle with almonds. Cool cake completely in pan on wire rack.