Preheat oven to 350 degrees F (175 degrees C).

Grease a 9-inch deep-dish pie plate.

Spoon 1 tablespoon of the buttermilk into a small bowl; place remainder of 1 cup buttermilk into a separate bowl.

Stir golden raisins into the larger amount of buttermilk and allow raisins to soak while you complete the remaining steps.

Spoon 1 tablespoon of the melted butter into the small bowl with the tablespoon of buttermilk; stir to combine and set aside. Set remaining melted butter aside.

Whisk together flour, sugar, baking powder, baking soda, and salt in a bowl.

Make a well in the center of the dry ingredients, pour in reserved butter, and stir until the mixture resembles coarse crumbs.

Mix the egg into the flour mixture until thoroughly combined.

Mix the soaked raisins with buttermilk into dough and shape dough into a ball.

Place the ball of dough into prepared pie dish and lightly pat dough down so top is slightly domed.

Use a sharp knife to cut two crisscrossing lines through the center of the loaf about 1/4 inch deep.

Thoroughly brush buttermilk and butter mixture over the loaf, getting the mixture into the crevices.

Bake in the preheated oven until loaf is golden brown and a toothpick inserted into the center comes out clean, 55 minutes to 1 hour.