Preheat oven to 350°F. Line cupcake pans with liners.

Whisk salt, baking powder, and flour in a medium bowl. Set aside.

Cream sugar into melted butter with a hand mixer until smooth. Beat in eggs one at a time, then stir in vanilla extract.

Alternately add dry ingredients and buttermilk to the wet mixture, starting and ending with dry ingredients. Gently mix until combined, scraping sides if needed. Fold in sprinkles.

Pour batter into cupcake liners, filling 2/3 full. Bake for 14-17 minutes or until a toothpick comes out clean. Cool completely before frosting.

To make frosting, beat softened butter until creamy. Gradually add powdered sugar and salt, blending well. Mix in vanilla and heavy cream until smooth and fluffy.

Frost cooled cupcakes as desired. Decorate with additional sprinkles if preferred.