Ingredients
1 package (18.25 oz) yellow cake mix
160 ml water
3 eggs
115 g butter, softened
320 g packed brown sugar
15 ml ground cinnamon (or to taste)
15 ml vanilla extract
340 g butter
540 g all-purpose flour
15 g confectioners' sugar for dusting
Directions
Step 1
Prepare all the ingredients.
Step 2
Preheat the oven to 175°C. Grease a 30x45 cm jellyroll pan.
Step 3
Using an electric mixer, beat together the yellow cake mix, water, eggs, and 115 g softened butter in a mixing bowl until well combined (about 2 minutes on medium speed). Pour the cake batter into the prepared jellyroll pan.
Step 4
Bake in the preheated oven until the edges of the cake are light brown but the middle is still slightly gooey, for 15 to 17 minutes.
Step 5
While the cake is baking, mix the brown sugar, cinnamon, vanilla extract, 340 g butter, and flour together in a large bowl until the mixture forms medium crumbs.
Step 6
Remove the cake from the oven and press about 3/4 of the crumb topping onto the almost-baked cake. Reserve the remaining topping.
Step 7
Return the cake to the oven and bake for an additional 10 to 12 minutes, until the crumb topping is firm and the cake is fully cooked.
Step 8
Take the cake out of the oven, sprinkle with the remaining crumb topping, and let it cool to room temperature. Sprinkle with confectioners' sugar before serving.