Preheat your oven to 350 degrees. Grease your bundt pan with coconut oil or butter and set aside.

In a large mixing bowl whisk together the gluten free flour, baking powder, baking soda and salt. Reserve 1/4 cup for streusel filling.

In the bowl of your stand mixer add the unsalted butter, granulated sugar and brown sugar. Beat together until combined and starting to stick to the sides of the mixing bowl. Add the eggs, sour cream and vanilla and beat until well mixed together, about 2-3 minutes.

Add the dry ingredients to the wet ingredients (don't forget to reserve 1/4 cup of the dry mixture!) and blend together until a smooth batter forms, about 1-2 minutes.

In a small mixing bowl whisk together the reserved dry cake mixture, brown sugar, cinnamon and pecans.

In your greased bundt pan pour about 1/3 of the cake batter. Be sure the entire bottom the pan is covered. Then spoon the streusel filling over top. Next, add the rest of the cake batter covering the streusel filling completely.

Bake at 350 degrees for 45-50 minutes. The cake will be browned and pulling away from the sides of the pan when it's done.

Let the cake stand for 10 minutes in the pan and then flip onto a cooling rack to cool completely before glazing.

For the glaze, in a mixing bowl add the powdered sugar, milk and vanilla. Beat with a whisk until a smooth glaze forms.

Pour the glaze over the cake and serve.