Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans or line them with parchment paper.

In a large bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.

In another bowl, beat the softened butter and sugar until light and fluffy.

Add eggs one at a time, mixing well after each addition.

Stir in the vanilla extract.

Gradually alternate adding the dry ingredients and buttermilk, mixing until smooth.

Divide the batter evenly between the prepared cake pans.

Bake for 30–35 minutes or until a toothpick inserted in the center comes out clean.

Let the cakes cool in the pans for 10 minutes, then transfer to a wire rack to cool completely.

Beat the softened butter until creamy.

Gradually add powdered sugar, mixing well.

Add heavy cream and vanilla extract, then beat until fluffy.

If using food coloring, divide the frosting into separate bowls and mix in desired colors.

Place one cake layer on a serving plate and spread a layer of frosting.

Add the second cake layer and cover the entire cake with frosting.

Use piping bags and decorating tips to create designs.

Add sprinkles, edible glitter, fondant, or themed cake toppers to match your desired theme.

Slice and serve your beautifully decorated DIY Themed Birthday Cake at your celebration.