Grease and flour an 8x8 pan and set aside
Make the Topping:
Mix together ¼ Cup Sugar and Cinnamon in a small bowl and reserve.
In a large bowl, with a sturdy spatula or hand mixer, cream together 1 cup sugar and the butter until pale yellow and incorporated.
Add eggs one at a time, beating well after each addition until batter is pale yellow in color
Add vanilla extract and mix well.
In a medium bowl, combine gluten free flour, baking powder, and baking soda and whisk well to combine.
Add half of the flour mixture alternately with the sour cream to the wet ingredients and mix well after each addition, scraping the bowl as needed.
Repeat with the remaining flour and sour cream.
Preheat the oven to 350ºF.
Place half of the batter into prepared pan and spread evenly in the pan. Sprinkle half of the sugar and cinnamon mixture over the batter.
Repeat the layers with the remaining batter and sugar-cinnamon mixture.
Bake for 40-45 Minutes until a toothpick comes out clean when inserted into the cake.
Cool cake in pan before cutting and serving.
Store cake in an air tight container at room temperature.