Preheat the oven to 350°F. Lightly grease a 9- or 10-cup bundt-style pan., In a medium bowl, combine the flour, baking powder, baking soda, and salt., In a separate bowl, beat together the butter and brown sugar until light and fluffy., Add the eggs one at a time, beating for a minute or two and scraping the sides and bottom of the bowl between additions. Mix in the maple syrup., Add half the flour mixture, followed by the sour cream, vanilla, and maple flavor, and finally the remaining flour mixture. Mix until just combined, scraping the sides and bottom of the bowl between each addition., Scoop the batter into the prepared pan, and bake for 45 to 50 minutes, until a cake tester or toothpick inserted in the center comes out clean., Allow the cake to cool for 10 minutes in the pan, then turn it out onto a serving plate., While the cake is cooling combine the glaze ingredients in a medium saucepan. Bring the glaze to a rapid boil, then reduce to a simmer and cook for about 5 to 8 minutes, until it thickens to a syrupy consistency. Remove the pan from the heat., Brush the hot glaze over the warm cake. Allow the cake to cool completely before serving., Store, unsliced, at room temperature for several days; freeze for longer storage.