Heat the oven to 350°F (175°C). Grease two 6-inch round cake pans and line the bottoms with parchment.

Whisk the flour, baking powder, and salt together in a medium bowl.

Beat the softened butter and granulated sugar for 2–3 minutes, until pale and fluffy.

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

Add the dry ingredients in two or three additions, alternating with the milk. Mix only until combined, then fold in the sprinkles if using.

Divide the batter evenly between the prepared pans. For matching layers, weigh the batter and place approximately half in each pan.

Bake for 25–30 minutes, until the tops spring back lightly and a toothpick inserted in the center comes out clean or with a few moist crumbs.

Cool the cakes in their pans for 10 minutes. Turn them out onto a rack and cool completely.

For the buttercream, beat the softened butter until smooth. Gradually add the sifted confectioners’ sugar, then mix in the vanilla, salt, and enough cream or milk to make a smooth, spreadable frosting.

Level the cakes if needed, fill and frost with the buttercream, and decorate with additional sprinkles.