Preheat your oven to 350°F (175°C) and grease and flour a 9x5 inch loaf pan.

In a medium bowl, combine all-purpose flour, baking powder, baking soda, and salt. Whisk to blend, then set aside.

In a large mixing bowl, whisk together melted butter and granulated sugar until smooth. Beat in eggs one at a time, followed by vanilla extract and buttermilk.

Gradually fold the dry ingredients into the wet mixture, mixing just until combined.

Gently fold in the sprinkles, being careful not to overmix.

Pour the batter into the prepared loaf pan and smooth the top. Optionally sprinkle with coarse sugar or more sprinkles.

Bake for 45-55 minutes, checking for doneness with a toothpick around the 40-minute mark.

Allow the loaf to cool in the pan for 10-15 minutes before transferring it to a wire rack to cool completely.