In a medium bowl, whisk together 2 cups of all-purpose flour, 2 teaspoons of baking powder, ½ teaspoon of baking soda, ½ teaspoon of salt, and ½ teaspoon of ground nutmeg for about 30 seconds.

In another large bowl, mix together ½ cup of melted unsalted butter, 1 cup of granulated sugar, 2 large eggs, 1 cup of buttermilk, and 1 teaspoon of vanilla extract. Stir until the mixture is smooth.

Gradually pour the wet mixture into the dry ingredients, stirring gently with a spatula just until combined.

Preheat your oven to 350°F (175°C) and grease or flour a 9x13 inch baking pan.

Pour the batter into the prepared baking pan and bake for 20-25 minutes, or until the edges turn golden.

Once baked, remove the pan from the oven and let it cool in the pan for 10 minutes before transferring to a wire rack.

In a mixing bowl, sift 1 cup of powdered sugar and whisk in ¼ cup of pure maple syrup, 2 tablespoons of milk, 2 tablespoons of melted butter, ½ teaspoon of vanilla extract, and a pinch of salt.

Once the maple donut bars have cooled, pour the glaze over them and use a spatula to spread it evenly.

Allow the glaze to set for 30-60 minutes before cutting the bars into squares.