Step 1

Prep the pan: Preheat the oven to 350°F. Line an 8×8-inch metal cake pan with aluminum foil or parchment paper (for easy release) and spray with cooking spray.

Step 2

Make the cake batter: In a large bowl, combine the butter and sugar and use a wooden spoon to smash the butter and break it up into the sugar. Without a mixer, it is difficult to properly cream the mixture until you add in the egg, and that’s OK!

Step 3

Add the egg, then whisk vigorously until the mixture is completely smooth, 2-3 minutes.

Step 4

Add the flour, baking powder and salt and mix gently, stopping before the flour is completely incorporated. Add the vanilla and then slowly add in the milk while whisking. Whisk just enough to incorporate the milk.

Step 5

Make the topping: Combine the flour, brown sugar and cinnamon in a bowl. With your hands, work in the cold butter until the mixture has a homogeneous crumbly texture.

Step 6

Pour two-thirds of the batter into the prepared pan. Spread half the topping over the batter (try to distribute it evenly). Add the remaining batter and top with the rest of the topping.

Step 7

Bake for 38-42 minutes, until a toothpick inserted in the center comes out clean. Let cool completely before serving.