Preheat your oven to 350°F (175°C) and prepare a loaf pan by lining it with parchment paper or greasing it.

In a medium bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt.

In a large bowl, cream the melted unsalted butter and granulated sugar together until smooth and fluffy.

Add the eggs one at a time to the butter and sugar mixture, mixing well after each addition. Stir in the vanilla extract and buttermilk.

Slowly combine the dry ingredients into the wet mixture, stirring gently until just mixed.

Fold in the red and green sprinkles carefully.

Transfer the batter to the prepared loaf pan, smoothing the top and adding coarse sugar if desired.

Bake for 45-55 minutes until a toothpick comes out clean. The top should be golden brown.

Cool in the pan for 10-15 minutes, then transfer to a wire rack to cool completely before slicing.