Preheat the oven to 325°F

Line a 9x9 inch aluminized steel cake pan with parchment paper or grease with baking spray. Set aside. (Note: This recipe was not tested in a glass cake pan).

Make the crumb topping first: whisk together 1 ½ cups of flour, both sugars, cinnamon and salt. Mix in the melted butter until mostly combined. Then slowly add in the remaining 1 cup flour until large crumbles form. I like to use my fingers to make large clumps and careful not over mix. Set aside.

Make the cake next: whisk together the cake flour, baking powder, baking soda, cinnamon and salt in a medium sized mixing bowl. Set aside.

Using a stand mixer fitted with the paddle attachment, cream the softened butter and granulated sugar until creamy and fluffy. About 3 minutes on medium high speed. Scrape down the sides once or twice as needed.

Turn the mixer down to medium low speed and add in the eggs. Then, add in the sour cream, milk, oil and vanilla. The batter will look curdled at this point but it's ok.

Add in the dry ingredients on low speed. Stopping to scrape down sides of bowl as needed. Batter will be thick.

Spread into the prepared pan. Tap the cake on the counter a couple times to release any air bubbles.

Add the crumb topping, keeping most of the crumbs large and whole, and press down gently.

Bake for 45-50 minutes or until a toothpick inserted in the very middle comes out clean. Careful not to over bake.

Let cool in the pan completely. Dust powdered sugar on the top. Slice and enjoy! (I think this is best enjoyed the very first or second day. And I love popping it in the microwave for a few seconds to get warm again!)