Make the Donut Bars:

Preheat Oven: Preheat your oven to 350°F (175°C). Grease and line a 9x13-inch baking pan with parchment paper, leaving an overhang for easy removal.

Combine Dry Ingredients: In a large bowl, whisk together the flour, granulated sugar, brown sugar, baking powder, salt, nutmeg, and cinnamon.

Mix Wet Ingredients: In a separate bowl, whisk together the melted butter, milk, eggs, and vanilla extract.

Combine Wet and Dry: Gradually add the wet ingredients to the dry ingredients, stirring until just combined. Do not overmix.

Bake: Spread the batter evenly into the prepared pan. Bake for 15-18 minutes, or until a toothpick inserted into the center comes out clean. Let the bars cool completely in the pan.

Make the Maple Glaze:

Prepare the Glaze: In a small saucepan, melt the butter over medium heat. Add the maple syrup and bring to a gentle simmer. Remove from heat and whisk in the powdered sugar, vanilla extract, and a pinch of salt until smooth.

Glaze the Bars: Once the bars are cool, remove them from the pan using the parchment overhang. Spread the maple glaze evenly over the top.

Serve:

Cut and Serve: Allow the glaze to set for 10-15 minutes, then slice into rectangular bars. Serve immediately.