In a medium bowl, whisk together the flour, baking powder, cinnamon, and salt. Mixing these first ensures your batter bakes evenly without clumps or bitter spots.
In a separate larger bowl, whisk the milk, melted butter, sugar, eggs, and vanilla. You want a smooth, creamy texture here. I like to whisk the eggs first before adding the rest—it keeps things lump-free.
Slowly pour the dry ingredients into the wet mixture while stirring gently. Be careful not to overmix; this helps keep the bread soft and fluffy.
Dice the apples evenly so they bake uniformly. Then mix them with cinnamon and sugar in a small bowl. Let it sit for a minute—it brings out the juices and softens the fruit a little.
Pour half the batter into your greased loaf pan. Add half the apple mixture on top. Spread the rest of the batter, then layer the remaining apples. Gently press the apples down into the top layer so they don’t burn while baking.
Place the loaf pan in the oven and bake at 350°F (175°C) for 50 to 60 minutes. Check doneness with a toothpick—it should come out clean. Let the bread cool in the pan for 10 minutes, then move to a wire rack.
Once fully cooled, whisk together powdered sugar, milk, and vanilla. Adjust the milk to get the consistency you like—thick or drizzle-thin. Drizzle the glaze over the bread and let it set before slicing.