1-Begin by preheating the oven to 350°F (175°C), which helps the cake rise evenly. Prepare an 8-inch square pan by lining it with parchment paper or greasing it lightly. This ensures your cake releases easily and maintains its shape.

2-Making the crumb mixture is next combine the brown sugar, flour, cinnamon, and cold butter until it forms a crumbly texture, then pop it in the fridge. In another bowl, whisk together the flour, baking powder, baking soda, and salt to get your dry ingredients ready.

3-Now, beat the softened butter and granulated sugar until they’re creamy and smooth, which usually takes a couple of minutes. Add the eggs one at a time, mixing well after each, then stir in the vanilla extract for that extra flavor boost.

4-Mix in the sour cream to keep the cake tender and moist, then gently fold in the dry ingredients. Finally, add the milk to help with spreading, as the batter can be thick. This step-by-step approach prevents overmixing and keeps the texture light.

5-Spread half of the batter into your prepared pan, then sprinkle half of the crumb mixture on top. Add the remaining batter and smooth it out gently, finishing with the rest of the crumbs. Bake for 35-40 minutes, or until a toothpick inserted in the center comes out clean.

6-Let the cake cool for 15 minutes before you slice it. If you want, prepare the vanilla icing by mixing confectioners’ sugar, vanilla extract, and heavy cream or milk, then drizzle it over the warm cake.