Preheat the oven to 350 degrees and grease a small loaf pan.

In a mixing bowl, stir together the flour, granulated sugar, baking powder, and 1 teaspoon ground cinnamon.

Add the diced apple, egg, melted butter, milk, and vanilla extract. Mix until a thick batter forms.

Pour half the batter into the prepared pan. Sprinkle the brown sugar evenly over it, then top with the remaining batter.

Bake for 35 to 40 minutes until a toothpick inserted in the center comes out clean. Cool in the pan for 10 minutes.

Stir the powdered sugar with enough water to make a thin glaze, then add the red food coloring. Drizzle over the cooled cake.