Preheat your oven to 350°F. Grease a 12x17 or 12x18-inch baking pan to ensure your cake comes out easily after baking.

Chop the apples into small pieces and set them aside.

Whisk together in a large bowl the flour, granulated sugar, baking soda, salt, and ground cinnamon.

Melt the butter and water in a saucepan over medium heat, bringing it to a simmer.

Pour this warm mixture over the dry ingredients and mix until just combined.

Stir in sour cream and eggs until everything is well mixed.

Fold in the chopped apples gently, ensuring they are evenly distributed throughout the batter.

Pour the batter into the prepared pan, spreading it out evenly.

Bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean. Allow it to cool in the pan for 1 hour.

Prepare the icing by melting butter, brown sugar, and heavy cream in a saucepan over medium heat, bringing it to a boil.

Remove from heat and whisk in powdered sugar and vanilla extract until smooth.

Pour the icing over the cooled cake, spreading it evenly with a spatula. Allow it to set for 20-30 minutes before serving.