Set the oven to 350°F (175°C). Grease and flour a 9x5-inch loaf pan. Peel and chop the apples into bite-sized pieces. Set aside.
In a large bowl, whisk together flour, sugar, baking powder, and salt.
In another bowl, mix melted butter, eggs, milk, and vanilla extract until smooth. Pour the wet ingredients into the dry ingredients and stir until just combined. Don’t overmix.
Pour half of the batter into the loaf pan. Top with half of the chopped apples and cinnamon-sugar. Repeat with the remaining batter, apples, and cinnamon-sugar.
Bake for 60 minutes, or until a toothpick comes out clean. Cover with foil if the top browns too quickly.
Whisk powdered sugar and milk (or cream) until smooth, adjusting the consistency as desired.
Let the bread cool in the pan for 10 minutes, then transfer to a wire rack to cool completely. Drizzle the glaze over the cooled bread and slice into generous pieces.