Beth's Cinnamon Crumb Coffee Cake
Tender buttermilk cake with a cinnamon-brown sugar filling and crispy streusel topping that stays moist for days. The secret: cold butter and buttermilk.
Ingredients
For the Streusel Topping
- 0.75 cup all-purpose flour
- 0.5 cup brown sugar packed
- 1.5 tsp ground cinnamon
- 0.125 tsp salt pinch
- 6 tbsp cold butter cut into small cubes
For the Cake Batter
- 1.5 cup all-purpose flour
- 1.5 tsp baking powder
- 0.5 tsp baking soda
- 0.25 tsp salt
- 6 tbsp butter softened
- 0.75 cup sugar granulated
- 2 large eggs
- 1 tsp vanilla extract
- 0.75 cup buttermilk
For the Cinnamon-Brown Sugar Filling
- 0.33 cup brown sugar packed
- 1 tbsp ground cinnamon
Instructions
- Make the streusel topping first: combine flour, brown sugar, cinnamon, and a pinch of salt in a small bowl.
- Add cold butter cubes to the streusel mixture and work it in with your fingertips, pressing and rubbing until the mixture resembles coarse breadcrumbs with some pea-sized pieces of butter visible. Some larger chunks are good — they create visible crumbs in the finished cake.
- Refrigerate the streusel while you make the batter; cold streusel sits on top of the batter instead of sinking into it.
- In a bowl, whisk together flour, baking powder, baking soda, and salt for the cake batter.
- In a separate bowl, beat the softened butter and sugar together until light and pale, about 2 minutes.
- Add eggs one at a time to the butter-sugar mixture, beating after each addition until incorporated.
- Add vanilla extract to the batter and mix until combined.
- Alternate adding the flour mixture and buttermilk to the batter in three additions, beginning and ending with flour. Mix on low speed just until combined — stop as soon as no dry streaks remain. Do not overmix, as this develops gluten and makes the cake tough.
- Grease a 9x9-inch baking pan and pour half the batter into it, spreading evenly.
- Combine brown sugar and cinnamon for the filling, then sprinkle the cinnamon-brown sugar mixture evenly across the batter layer.
- Pour the remaining batter over the cinnamon layer and spread gently to cover without disturbing the filling.
- Scatter the cold streusel topping evenly across the top of the batter. Do not press it in — let it sit loosely on the surface.
- Bake at 350°F for 35 to 40 minutes, until the streusel is deeply golden, the edges are pulling from the pan, and a toothpick inserted in the center (avoiding the cinnamon layer) comes out with just a few moist crumbs.
- If the streusel is browning too fast before the center is done, tent the pan loosely with foil for the last 10 minutes of baking.
- Cool the cake in the pan for at least 15 minutes before cutting — the cinnamon layer needs time to set so it holds the layers together.
- Cut into 9 squares. Serve warm or at room temperature with coffee, espresso, or tea.
Notes
Keep the streusel cold and refrigerate it while making the batter — warm streusel sinks into the batter instead of staying crispy on top. Don't overmix the batter; stop as soon as no dry streaks remain, as overmixing develops gluten and makes the cake tough. Insert the toothpick test into the cake portion only, avoiding the cinnamon filling layer which will always look wet. Cool the cake for at least 15 minutes before cutting so the cinnamon layer can set and hold the cake together.