Oven to 160 degrees C, bottom heat if possible, otherwise preheat top / bottom heat. Lightly grease 2 donut molds.
In a large bowl, mix the flour, sugar, baking powder, nutmeg, cinnamon and salt together. In a smaller bowl, mix the buttermilk, eggs, vanilla extract and melted butter together well.
Then add the wet ingredients to the dry ones and mix well. Fill the donut molds 3/4 full and put the molds in the oven. Bake the donuts for 8 to 10 minutes until they are light golden brown.
Let the donuts cool down a little in the mold, then remove them from the mold.
Prepare the topping:
Mix the sugar and cinnamon in a small bowl. First dip each donut in the melted butter and then roll it in the sugar / cinnamon mixture.