Preheat oven to 180 C. Grease a 12-hole muffin tin or a plain cake tin.
In a large bowl, whisk together flour, baking powder, salt and nutmeg. In a separate bowl, cream together 100g sugar and butter. Beat in egg. Stir flour mixture into butter mixture alternately with milk. Beat well. Spoon into prepared muffin tin.
Bake in preheated oven for 20 to 25 minutes. While muffins are baking, combine 100g sugar and 1 teaspoon cinnamon powder.
Remove muffins from oven and muffin tin. Immediately, dip the tops of the muffins into the melted butter, then into the sugar/cinnamon mixture. Repeat with each muffin, until all muffin tops are covered. Serve warm.