Prepare the oven by preheating it to 350°F (175°C). Grease and line the bottoms of three pans that are 8 inches round.
In a bowl, combine flour, sugar, baking powder, and salt.
Mix the butter until it’s smooth. Add the eggs one by one, and then stir in the vanilla.
Add milk and dry mix, alternately. Be sure to scrape the bowl in between each addition.
Divide the batter evenly into the prepared pans and bake for 22–25 minutes. To check if the cakes are done, insert a toothpick into the center.
Cool cakes for 20 minutes, then level the tops. From the middle layer, cut out the center to form a well.
Fill the well with confetti, stack the layers, and crumb coat with buttercream.
Chill for 30 minutes. Finish with a smooth coat and gently press edible flowers onto the sides and top.
Slice to reveal color inside.