Preheat oven at 350-degrees. Grease a 9-or-10-cup bundt pan.
In a medium bowl, sift together the cake flour, baking powder, baking soda, and salt. Set aside.
In a big mixing bowl, beat together the butter and brown sugar until light and fluffy. Add eggs one at a time, scraping sides of bowl in between. Pour in the maple syrup.
Mix in half the flour mixture. Then stir in the sour cream, vanilla, and maple flavor. Add the rest of the flour mix, until everything is just combined.
Pour into the prepared pan. Bake for 45 to 50 minutes, until a cake tester inserted into the middle comes out clean. Let cool on rack for 10 minutes, then invert the cake onto the rack. Don't wash the pan! Set it aside for now.
After an hour and a half--or longer--begin making the glaze. In a medium saucepan, combine all three glaze ingredients. Bring it a rapid boil, then reduce to a simmer for 5 to 8 minutes, until it thickens to a syrupy consistency. Remove pan from heat.
Carefully invert the cooled cake into the pan again. Use a chopstick or skewer to stab all over the cake. Slowly spoon or pour about half the glaze into the holes and edges. Let it rest a few minutes. Invert the cake again onto the cake pan base or a storage plate. Again, stab the top of the cake to create holes, then spoon the rest of the glaze on. Can also use a basting brush to cover the exterior of the cake and sweep up any drippings.
Store cake covered at room temperature. Slices can also be frozen.
OM NOM NOM!