Preheat oven to 350°. Prepare Twisted Doughnut Pan with nonstick cooking spray.
In the bowl of an electric mixer, beat butter and sugar until light and fluffy, about three minutes. Add eggs one at a time, mixing well after each. Add vanilla extract.
In another bowl, stir together flour, baking soda, nutmeg and salt. Add half dry ingredients and mix until nearly combined. Add buttermilk and remaining dry ingredients, mixing until incorporated. Do not overmix. .
Fill cruller cavities 2/3 full. Bake 18-22 minutes, or until a toothpick inserted in center of donut comes out clean. Cool in pan 5 minutes; remove to cooling rack.
For Confectioners' Sugar Glaze
In a large bowl, whisk all ingredients together until incorporated; dip crullers in glaze. Glaze will harden in 10-15 minutes.
For Cinnamon Sugar Topping
Stir together granulated sugar and ground cinnamon. Dip crullers in melted butter and sprinkle all over with cinnamon sugar mixture.