Preheat the oven to 350 degrees. Coat a 10-inch tube pan with cooking spray.
In a large mixing bowl with an electric mixer or in a stand mixer fitted with the paddle attachment, cream the butter alone for 3-4 minutes until light and pale.
Add sugar, creaming for an additional 2 minutes.
Add the eggs 1 at a time, then add the vanilla and sour cream.
In a medium mixing bowl, sift together cake flour, baking powder, baking soda, and kosher salt.
Add dry ingredients in 3 increments, only mixing until just combined. Do not over mix.
For the streusel, place the brown sugar, flour, cinnamon, salt, and butter in a bowl. Mash with a fork to combine. Set in refrigerator until ready to use.
Pour half the batter into the prepared tube pan, tapping to evenly distribute. Sprinkle with 3/4 cup streusel. Spoon the rest of the batter in the pan, spreading it out to cover the middle streusel layer. Top with remaining streusel.
Bake for 50 to 60 minutes, until it passes the toothpick test.
Let cool on a wire rack for at least 30 minutes. Carefully transfer the cake, streusel side up, onto a serving plate.
Whisk powdered sugar and maple syrup together, adding a few drops of water or milk if necessary, to make the glaze runny. Drizzle over cake before serving.
If you've tried this recipe, come back and let us know how it was!