Preheat your oven to 350°F (175°C). Grease and flour an 8-inch round or square cake pan, or line it with parchment paper for easy removal.

In a medium-sized bowl, whisk together the all-purpose flour, baking powder, and salt. Set this aside for now.

In a large bowl, use an electric mixer to beat the unsalted butter and granulated sugar until light and fluffy, about 3-4 minutes. This step helps to incorporate air into the batter, giving your cake a light texture.

Add the eggs, one at a time, beating well after each addition. Stir in the vanilla extract. Mix until fully combined.

Gradually add the dry ingredients to the wet ingredients in two parts, alternating with the whole milk. Start and end with the dry ingredients. Mix gently until just combined — avoid overmixing to keep the cake light and fluffy.

In a separate bowl, combine the melted butter, brown sugar, and vanilla extract. Stir in the cornflakes or rice cereal until they are well coated. If you're using cinnamon, add it here for a warm, spiced note.

Pour the cake batter into the prepared pan and spread it out evenly. Then, evenly distribute the crunch topping over the batter. The topping will crisp up as it bakes, creating a delicious contrast with the soft cake.

Place the cake in the preheated oven and bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean. The top should be golden and slightly crunchy.

Let the cake cool in the pan for 10 minutes before transferring it to a cooling rack. Once cooled, slice and serve. You can enjoy it as is, or drizzle a simple glaze on top for extra sweetness.