Prepare the Apples: Peel, core, and dice apples into small chunks. Toss with cinnamon and a sprinkle of sugar.
Mix Dry Ingredients: In a large bowl, whisk together flour, brown sugar, baking powder, cinnamon, and salt.
Combine Wet Ingredients: In a separate bowl, whisk together eggs, milk, melted butter, and vanilla extract.
Mix the Batter: Gradually add wet ingredients to dry ingredients, stirring until just combined. Fold in the spiced apples.
Fill the Muffin Tin: Spoon batter into a greased or lined muffin tin, filling each cup about 3/4 full.
Bake: Bake at 350°F (175°C) for 20-25 minutes, until golden brown and a toothpick comes out clean.
Glaze the Muffins: Whisk powdered sugar and milk to make the glaze. Drizzle over warm muffins.