Preheat oven to 350°F (175°C).
Prepare two 9x5-inch loaf pans—grease one and leave the other ungreased.
Mix brown sugar and cinnamon in a small bowl.
In a large bowl, cream together butter and granulated sugar until fluffy.
Beat in eggs one at a time. Add vanilla and mix.
In a separate bowl, whisk flour, baking powder, and salt. Add to butter mixture.
Mix in milk until batter is smooth.
In the ungreased pan, layer half the batter, then half the apples, half the cinnamon sugar, and drizzle 2 tbsp maple syrup.
Repeat layers with remaining ingredients.
Scoop the layered batter into the greased pan using a large spoon or scoop.
Bake 50–60 minutes, or until a toothpick comes out clean.
Cool 5 minutes, then remove from pan and cool 15 minutes more.
Whisk glaze ingredients and drizzle over warm loaf.