In a spacious mixing bowl, combine the all-purpose flour, baking soda, baking powder, salt, and ground nutmeg. Whisk them together nicely to ensure an even distribution.

In another bowl, whisk together the granulated sugar and eggs until smooth. Then, add in the buttermilk and melted unsalted butter, mixing until the mixture is well combined.

Gradually add the dry ingredients to the wet mixture, stirring gently. Be careful not to overmix; you want the dough to be tender.

Turn the dough out onto a floured surface. Using a floured rolling pin, roll the dough to about 1/2 inch thick. Use a donut cutter or two different-sized round cutters to cut out the donuts.

In a large pot or deep skillet, heat about 2 inches of vegetable oil over medium heat. To check if the oil is ready, drop a small piece of dough into the oil; if it sizzles and rises, it's ready for frying.

Gently place the donuts into the hot oil, but don’t overcrowd the pot. Fry until golden brown, about 2-3 minutes on each side. Use a slotted spoon to remove the donuts and place them on paper towels to drain excess oil.

Allow the donuts to cool slightly before dusting with powdered sugar or your favorite glaze. Serve warm for the best experience!