Preheat oven to 350°F degrees.
Line baking pan with parchment paper.
Whisk flour, baking powder, and baking soda.
Add salt and cinnamon to mixture.
Cream butter and sugars until fluffy.
Add eggs one at a time.
Mix in vanilla and maple syrup.
Alternate mixing flour and buttermilk.
Pour batter evenly into pan.
Bake until center springs back.
Cool bars completely before glazing.
Simmer maple syrup in saucepan.
Whisk powdered sugar with warm syrup.
Add milk for smooth glaze texture.
Pour glaze over cooled bars.
Let glaze set before slicing.