Preheat your oven to 350 degrees Fahrenheit. Make sure it’s fully heated before you place your cake in, as this will help it bake evenly and rise beautifully.
Grease and flour a 9×13-inch baking pan. This prevents the cake from sticking and allows for easy removal once baked, ensuring the perfect presentation.
Prepare the crumb topping by combining brown sugar, flour, and butter in a medium bowl. Cut the butter into the mixture using your fingers or a pastry cutter until no large pieces remain. This creates that lovely crumble.
Stir in the chopped macadamia nuts and white chocolate chips into the crumb topping mixture, ensuring an even distribution for maximum flavor in every bite. Set this mixture aside.
Make the batter by beating the softened butter, granulated sugar, and light brown sugar together in a large bowl using an electric mixer. Mix until it’s well combined and fluffy, about 3 to 5 minutes.
In another bowl, whisk together the all-purpose flour, baking powder, cinnamon, and salt. Gradually beat this dry mixture into the butter and sugar until fully incorporated.
Slowly add the milk, egg, and vanilla extract to the batter. Beat the mixture until smooth and well combined, ensuring a creamy texture.
Pour half of the batter into the prepared baking pan, spreading it evenly with a spatula. This layer will act as the base of your delicious cake.
Sprinkle half of the prepared crumb topping over the batter. This adds a lovely crunch that contrasts beautifully with the soft cake.
Spread the remaining batter over the topping, then sprinkle the rest of the crumb topping on top. This layering creates a delightful texture throughout the cake.
Bake in the preheated oven for 30 to 35 minutes, or until a toothpick inserted into the center comes out clean. Keep an eye on it as it bakes, enjoying the delicious smell wafting through your kitchen.
Once baked, let the cake cool in the pan for a few minutes before transferring it to a wire rack to cool completely. This step helps retain moisture.
Meanwhile, whisk together the powdered sugar, milk, and softened butter for the glaze. Drizzle it over the cooled cake for that final touch of sweetness.
