Preheat the oven to 175°C and grease and flour your baking pans.

In a large bowl, sift together the flour, sugar, baking powder, and salt.

In another bowl, beat the butter until fluffy. Add the eggs one at a time, beating well after each addition. Mix in the vanilla extract.

Gradually add the dry ingredients to the butter mixture, alternating with milk until just combined.

Divide the batter into multiple bowls and add different colors of food coloring to each bowl, mixing until the colors are even.

Pour the colored batters into the prepared pans and bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean.

Allow the cakes to cool completely before removing from pans.

For the frosting, beat the butter until creamy. Gradually add the powdered sugar and vanilla, beating until light and fluffy. Divide into bowls and add different food colors.

Frost the cooled cake layers, stacking them to form a rectangular shape.

Roll out the fondant and color it to your desired Lego shades. Cut and shape the fondant to fit the cake, mimicking Lego bricks.

Place the fondant over the cake, smoothing it out and trimming any excess.

Make small circles out of leftover fondant for the Lego knobs and attach them to the top of the cake.

Decoratively place fondant cars around the cake for a playful finish.