Bake for 20 minutes while preparing the maple glaze.
Pour the maple syrup into a medium skillet and cook over medium heat until bubbly. Stir in the walnuts and pumpkin pie spice; continue stirring until syrup thickens slightly. When the first 20 minutes of baking is done, remove the cake from the oven and drizzle the maple-walnut glaze over the cake, gently spreading the walnuts around.
Return the cake to the oven and bake for 10 more minutes or until a toothpick inserted in the center comes out clean.
Allow cake to cool in the pan on a wire rack for 10 minutes. Run a sharp knife around the edge of the cake to release from pan, and remove pan sides from cake. Cool completely on wire rack. Slice and serve.