Caramel Apple Sheet Cake

Ingredients

• 2 cups all-purpose flour
• 1 teaspoon ground cinnamon
• 1/2 teaspoon baking soda
• 1/4 teaspoon salt
• 1 cup granulated sugar
• 1 cup light brown sugar, lightly packed
• 2 sticks unsalted butter
• 1 cup water
• 1/2 cup buttermilk
• 2 large eggs
• 1 teaspoon vanilla
• 2 cups Granny Smith apples, peeled and chopped
• 1 stick unsalted butter
• 1/4 cup milk
• 3 cups powdered sugar, sifted
• 1/2 teaspoon vanilla extract
• 1/4 cup salted caramel sauce, homemade or store-bought