Instructions
For the crumble topping, place the flour, pecans, brown sugar, butter, cinnamon, and salt in a food processor.
Whirl until the nuts are ground and the mixture is crumbly. Add the maple syrup and pulse until well combined.
Preheat oven to 350F. Butter and flour a 9" springform pan.
For the batter, whisk the flour, baking powder, baking soda, and salt together in a small bowl. In the bowl of a standup mixer with a paddle attachment, cream the butter and brown sugar together until light and fluffy. Add the maple syrup, maple extract, vanilla and mix well.
Add the eggs, one at a time, and beat after each addition. Add the flour mixture alternating with the sour cream, beginning and ending with the flour, mixing until just combined.
Spread half the batter into the prepared pan and sprinkle with half of the crumb mixture. Carefully spread the remaining batter over and again sprinkle with the crumb mixture.
Bake in the oven for 50-60 min. or until the tester comes out clean.
Let the cake cool for 5-10 min. on a cooling rack and then remove the sides of the springform pan. Let the cake continue to cool and when manageable remove the bottom of the pan and let cool completely on a cooling rack.
Sprinkle with confectioner's sugar just before serving. The cake can be made one day in advance wrapped in plastic wrap.
Adapted from Epicurious