For the Muffins:
3 cups unbleached all-purpose flour
1/4 teaspoon baking soda
2 1/2 teaspoons baking powder, preferably aluminum-free
3/4 teaspoon fine sea salt
1/4 teaspoon freshly grated nutmeg
1/4 teaspoon ground cardamom
3/4 cup plus 2 tablespoons whole milk
2 tablespoons buttermilk
8 tablespoons (1 stick) unsalted butter, at room temperature
3/4 cup sugar
2 large eggs
For the Doughnut Coating:
8 tablespoons (1 stick) unsalted butter, melted
1 cup sugar mixed with 1 tablespoon ground cinnamon
Recipe
To make the muffins: Position a rack in the lower third of the oven and preheat the oven to 350 degrees F. Lightly spray 12 large muffin cups with vegetable oil spray.
Sift together the flour, baking soda, baking powder, salt, nutmeg, and cardamom. In a medium bowl, combine the milk and the buttermilk.
In a large mixing bowl, using a handheld mixer on medium speed, cream the butter for 2 to 3 minutes. Turn the speed to low and gradually add the sugar. Continue to mix until the mixture lightens in color. Add the eggs one at a time, beating just until combined. Add the dry ingredients in thirds, alternating with the milk mixture, mixing just until smooth; do not over-mix.
With a large ice cream scoop or spoon, scoop the batter into the prepared muffin cups, filling them approximately two-thirds full. Bake for 20 to 25 minutes, until the tops are firm to the touch and lightly golden.
While the muffins bake, set up two bowls to dunk them in. In one bowl you will have the melted butter, and in the other bowl you will have the cinnamon sugar.
Let the doughnuts cool completely on a wire rack. Dunk them in melted butter, then coat them with the cinnamon sugar. The muffins can be stored in an airtight container for up to 2 days.