Make the cinnamon apples. Combine diced apples, brown sugar and cinnamon together in a medium small bowl and toss to combine. Set aside.

Bake the cake batter. Combine cooled melted butter, brown sugar, granulated sugar, egg, sour cream and vanilla in a large bowl and whisk until smooth.

Combine flour, baking powder and salt in a separate bowl and whisk to blend well. Add this to the bowl with the wet ingredients and fold it in gently. After a few strokes, it will be mostly combined but still rather lumpy and dry. Stop mixing and add the milk. Continue mixing gently until the batter just comes together smoothly.

Transfer half of the batter into the prepared pan and smooth it out. Spoon half the cinnamon apples over the batter and sprinkle half of the cinnamon brown sugar on top to cover the apples. Spoon the remaining batter over the apples and use an offset spatula to spread it out into an even layer. Top with the remaining apples and sprinkle over all of the rest of the cinnamon sugar.

Bake for 55-60 minutes until the cake is golden brown and a skewer inserted into the center comes out clean. Transfer pan to a wire rack and let it cool for at least 30 minutes before icing or slicing. If you slice it while still too warm, it may fall apart.

Make the glaze while the loaf cools. Combine powdered sugar, milk, vanilla extract and salt and whisk until smooth. Once the loaf has cooled sufficiently (it can be still slightly warm), drizzle the glaze over top and let it drip over the sides. Enjoy!