01 - 
                Preheat oven to 350 degrees Fahrenheit and lightly coat a 10×15 inch jelly roll pan with nonstick spray.
              
              
              
                02 - 
                In a medium saucepan, bring butter and water to a boil, stirring frequently to avoid burning. Remove from heat and let cool slightly.
              
              
              
                03 - 
                In a large bowl, whisk together flour, granulated sugar, salt, baking soda, and cinnamon.
              
              
              
                04 - 
                In a separate bowl, whisk together sour cream and eggs until fully combined.
              
              
              
                05 - 
                Add the sour cream mixture to the dry ingredients and stir to form a thick batter.
              
              
              
                06 - 
                Fold in the diced or grated apples until evenly distributed.
              
              
              
                07 - 
                Gradually stir in the cooled melted butter and mix until fully incorporated and batter loosens.
              
              
              
                08 - 
                Pour batter into the prepared pan and bake for 25 to 27 minutes, or until the center springs back when lightly touched.
              
              
              
                09 - 
                Remove from oven and allow cake to cool until just slightly warm.
              
              
              
                10 - 
                Combine butter and milk in a microwave-safe bowl and heat for 45 seconds, then in 15-second intervals until butter is melted. Whisk to combine.
              
              
              
                11 - 
                Add powdered sugar, vanilla extract, and caramel sauce to the bowl and whisk until smooth. Adjust consistency with more sugar or milk as needed.
              
              
              
                12 - 
                Pour icing over the slightly warm cake and spread evenly. Let set fully before slicing.
              
              
              
                13 - 
                Cut into squares and serve.