Preheat the oven to 350°F and lightly grease a 12-cup muffin tin with baking spray.

In a large bowl, stir together the flour, baking powder, salt, and nutmeg. Set aside.

In the bowl of a stand mixer fitted with the paddle attachment, cream together the ⅔ cup softened butter and 1 cup of the sugar on medium speed for 2 to 3 minutes. Add the eggs, one at a time, mixing on low speed until combined. Scrape the bottom and sides of the bowl.

With the mixer still on low speed, gradually add the flour mixture to the sugar mixture, alternating with the milk, beating well after each addition.

Fill the prepared muffin cups two-thirds full with the batter and bake until golden, about 18 to 20 minutes.

In a medium microwave-safe bowl, melt the 2 sticks of butter in the microwave for 1 to 2 minutes.

In a separate medium bowl, combine the cinnamon with the remaining 1 ½ cups sugar.

Dip the baked muffins in the melted butter, coating thoroughly, then coat with the cinnamon-sugar mixture.