Combine egg and sugar in a large mixing bowl; beat well. Add molasses, buttermilk, and butter; mix well.
Sift together flour, baking powder, soda, salt, and spices. Add to molasses mixture, blending well. Cover dough, and chill at least 1 hour.
Divide dough in half. Working with one portion at a time, place dough on a floured surface; roll to 1/4-inch thickness. Cut dough with a floured doughnut cutter.
Heat 3 to 4 inches of oil to 375°; drop in 3 or 4 doughnuts at a time. Cook 1 minute or until golden brown; turn and cook other side. Drain on paper towels. Repeat cutting and frying procedures with remaining dough.
Combine sugar and cinnamon; stir well. Roll doughnuts in cinnamon mixture until coated, if desired.
Oxmoor House Homestyle Recipes