Preheat your oven to 350°F (175°C) and line a 4-inch cake pan with parchment paper.

Cream softened butter and sugar for about 3 minutes until light and fluffy, then add egg and vanilla extract.

In a separate bowl, whisk together flour, baking powder, and salt, then gradually mix with wet ingredients alternating with milk.

Pour the batter into the cake pan and bake for 22-25 minutes until a toothpick comes out clean.

Cool the cake in the pan for about 10 minutes, then transfer to a wire rack to cool completely.

Slice the cake into 2-3 even layers using a cake leveler or sharp knife.

In a mixing bowl, beat softened butter, then add powdered sugar and a splash of vanilla extract and heavy cream.

Set aside one-third of the frosting for the exterior and color the rest with food coloring.

Layer your cake by spreading frosting between layers, applying a thin crumb coat, and refrigerating for 15 minutes.

Decorate with colored frosting and edible markers, adding sprinkles or fruit as desired.