Preheat oven to 350°F (175°C).
Prepare a 9x13 inch pan with parchment paper.
In a large skillet, melt 2 tablespoons of butter over medium heat. Add 3.5 cups of diced apples, 1.5 teaspoons of cinnamon, and 1/2 cup of brown sugar. Cook until the liquid has evaporated and the apples are sticky.
In a large mixing bowl, combine 2 1/4 cups of flour, 1 cup of granulated sugar, and 2.5 teaspoons of baking powder.
Add 12 tablespoons of unsalted butter to the dry ingredients and mix until the mixture resembles sand.
In a separate bowl, whisk together 3/4 cup of milk, 3 large eggs, and 0.5 teaspoon of alcohol-free vanilla extract.
Add the wet ingredients to the dry ingredients and mix until just combined.
Spread the batter evenly into the prepared pan.
Spoon the cooked apple mixture evenly over the batter.
Bake for 60-70 minutes or until a toothpick inserted into the center comes out clean.
Let the cake cool in the pan for 30 minutes before transferring it to a wire rack to cool completely.
Once the cake is cool, prepare the glaze by whisking together 3/4 cup of confectioners' sugar, 1.5-3 tablespoons of milk, and 0.5 teaspoon of alcohol-free vanilla extract.
Drizzle the glaze over the cooled cake.