Preheat your oven to 350°F (175°C) and position the rack in the center. Grease and flour two 9-inch round cake pans, or line them with parchment paper for easier removal.

In a medium bowl, whisk together the flour, baking powder, and salt.

In a large bowl, using an electric mixer, beat the butter until creamy. Gradually add the sugar, beating until fluffy and pale yellow.

Add the eggs one at a time, beating well after each addition, then mix in the vanilla.

With the mixer on low, gradually add the flour mixture alternating with the buttermilk, mixing until just incorporated.

Divide the batter evenly between the prepared pans. Bake for 25-30 minutes or until a toothpick comes out clean.

Allow the cakes to cool in the pans for 10-15 minutes before transferring to wire racks to cool completely.

For the frosting, beat butter until creamy, then gradually add confectioners' sugar and beat until incorporated. Add cream, vanilla, and salt, and beat until fluffy.

Once cakes are cooled, frost one layer, add the second layer, apply a crumb coat, chill, and then add the final layer of frosting.

Decorate with sprinkles, and personalize with a birthday message or candles just before serving.