Preheat oven to 350°.
To prepare the cake, combine the first 4 ingredients in a small saucepan over medium-high heat. Cook 5 minutes or until syrupy, stirring frequently; cool.
Lightly spoon flour into a dry measuring cup; level with a knife. Combine flour, baking soda, and salt in a small bowl, stirring well with a whisk. Combine granulated sugar and butter in a large bowl; beat with a mixer at medium speed until well-blended; add egg and extracts, beating well. Add flour mixture to sugar mixture alternately with buttermilk, beginning and ending with flour mixture; beat well after each addition.
Spoon the batter into an 8-inch round cake pan coated with cooking spray. Arrange apple mixture over cake. Sprinkle with almonds. Bake at 350° for 25 minutes or until cake begins to pull away from sides of pan. Cool in pan on a wire rack for 10 minutes.
To prepare glaze, combine powdered sugar, 1 teaspoon buttermilk, and 1/4 teaspoon vanilla in a small bowl; stir with a whisk. Drizzle glaze over cake. Serve warm or at room temperature.