In a large mixing bowl, combine the flour, baking powder, salt, and sugar. Mix until well incorporated.
In a separate bowl, whisk together the buttermilk and baking soda until blended.
Gradually add the wet ingredients to the dry ingredients, stirring just until combined. The dough will be lumpy; do not overmix.
Pour the melted butter into an 8x8-inch baking dish or a cast-iron skillet, ensuring it coats the bottom evenly.
Spoon the biscuit dough into the dish over the butter, using a spatula to spread it out if needed. The dough should be in a single layer but can be slightly uneven.
Bake for 15-20 minutes or until the top is golden brown and a toothpick inserted into the center comes out clean.
Let the biscuits cool for a few minutes before serving. Spoon some of the melted butter from the bottom over the top for extra richness.
Prep Time: 10 min | Total Time: 30 min | Servings: 8