Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking pan or line it with parchment paper.

In a medium bowl, whisk together the dry ingredients: all-purpose flour, baking powder, baking soda, ground nutmeg, and salt. Set aside.

In a large mixing bowl, cream together the softened butter and granulated sugar until light and fluffy. Add eggs one at a time, mixing well after each addition, then stir in vanilla extract.

Gradually add the dry mixture to the butter mixture, alternating with buttermilk. Mix until just combined.

Pour the batter into the prepared pan and spread evenly. Bake for 22-25 minutes or until a toothpick inserted comes out clean. Cool completely.

Prepare the glaze by melting unsalted butter in a saucepan until golden brown. Whisk in powdered sugar, maple syrup, and vanilla bean paste until smooth.

Once the bars are cooled, pour the glaze over the top. Let it set for 10-15 minutes before slicing into rectangles.