Step 1

Preheat oven to 350°F (177°C). Grease and lightly flour a round or square 8-inch pan. Or simply line with parchment paper.

Step 2

Combine the brown sugar, flour, and cinnamon together in a medium bowl. Cut in the chilled butter with a pastry blender or two forks (or even with your hands) until the mixture resembles pea sized crumbs. Set aside.

Step 3

Whisk the flour, baking powder, baking soda, and salt together in a large bowl. Set aside. Using a handheld or stand mixer fitted with a paddle attachment, beat the butter on high speed until smooth and creamy – about 1 minute. Add the sugar and beat on high speed for 2 minutes until creamed together fairly well. Scrape down the sides and up the bottom of the bowl with a rubber spatula as needed. On medium-high speed, add 1 egg at a time, beating well after each addition. Beat in the vanilla extract and sour cream. Scrape down the sides and up the bottom of the bowl with a rubber spatula as needed.

Step 4

With the mixer on low speed, beat in the dry ingredients until just combined. Do not overmix this batter. Scrape down the sides and up the bottom of the bowl with a rubber spatula as needed. The batter will be smooth and thick. Carefully spread half of the batter into the pan. Sprinkle with half of the streusel. Carefully spread the remaining half of the batter on top, then the remaining streusel. You need every last drop of batter to fill this pan. Do your best spreading it out into even layers. I use the back of a spoon to spread the batter around neatly.

Step 5

Bake for around 30 minutes or until the cake is baked through. To test for doneness, insert a toothpick into the center of the cake. If it comes out clean, it is done. Allow cake to cool in the pan set on a wire rack for 20 minutes.

Step 6

Whisk all of the glaze ingredients together in a medium bowl. Drizzle over cake. Slice and serve. Cover leftovers tightly and store at room temperature or in the refrigerator for up to 5 days.