Preheat your oven to 350°F (175°C) and grease two 9-inch round cake pans with unsalted butter or cooking spray. Line with parchment paper.

In a mixing bowl, whisk together the flour, baking powder, and salt until combined.

In a separate bowl, beat the butter and sugar together until light and fluffy.

Add the eggs one at a time and mix well after each addition, then mix in the almond extract.

Gradually add the dry ingredients and buttermilk to the butter mixture, starting and ending with the flour.

Divide the batter between the prepared pans and bake for 30-35 minutes, or until a toothpick comes out clean.

Let the cakes cool in the pans for about 10 minutes before transferring to wire racks to cool completely.

For the buttercream, beat the softened butter and confectioners' sugar together, adding heavy cream until spreadable.

Divide the buttercream and add gel colors to create your desired shades.

Apply a thin crumb coat of buttercream around the cooled cakes and then decorate with the rainbow petal pattern.