Preheat oven to 350℉. Line an 8 inch cake pan with parchment paper.
In a large bowl using an electric hand mixer, cream together butter and sugars. Add in sour cream, milk, egg and vanilla and mix to combine. Next sift in flour, cinnamon, baking powder, baking soda and salt and stir to combine. Transfer batter to your pan and spread out evenly.
Streusel:
In a small bowl, combine the flour, brown sugar and cold butter with your fingers. Combine gently to ensure you leave bigger crumbs. Sprinkle the crumble on top of the cake batter evenly. Bake for 40-45 minutes or until toothpick comes out clean. Allow cake to set in the pan for 10 minutes and then transfer to a wire rack to cool.
Icing:
In a small bowl, whisk together powdered sugar and milk until smooth. Allow cake to cool completely before drizzling the icing on top, in a zigzag motion.
Notes
Store leftovers in an airtight container on your counter for 3-4 days.
Instead of using sour cream, use Greek yogurt.
You can use a 9 inch cake pan for this recipe too just decrease the bake time by 5 minutes or so.
Nutritional information is for 1 slice and includes the streusel crumble and icing finish!