Preheat your oven to 325°F (163°C). Line an 8x8-inch baking dish with aluminum foil, leaving some overhang to help lift the cake later. Lightly grease the foil with nonstick spray.

In a medium saucepan over medium heat, melt 3 tablespoons of unsalted butter. Add the diced Honeycrisp apples, 3 tablespoons of light brown sugar, 1 teaspoon of cinnamon, and 1/4 teaspoon of kosher salt. Cook for 5-8 minutes until the apples soften slightly. Once done, remove from heat and set aside.

In a medium bowl, combine the melted butter, granulated sugar, 1 teaspoon of cinnamon, and salt for the crumb topping. Stir to combine. Add in the flour and mix until just combined.

In the bowl of a stand mixer, combine 1 3/4 cups of cake flour, 1/2 cup of granulated sugar, 1 teaspoon of cinnamon, 1/2 teaspoon of kosher salt, and 1/4 teaspoon of baking soda. Mix on low speed to incorporate. Add the room temperature butter and mix until there are no visible pieces. Then, add the buttermilk, whole egg, egg yolk, and vanilla extract. Mix until the batter is light and fluffy.

Pour the cake batter evenly into the prepared pan, smoothing the top. Spoon the cooked apple mixture over the batter, ensuring even distribution. Finally, crumble the topping over the apples evenly.

Place the pan in the preheated oven and bake for 55-60 minutes, or until the crumb topping is golden brown and a toothpick inserted into the center comes out with a few crumbs.

Allow the cake to cool in the pan for about 30 minutes. Then lift it out using the foil overhang. Drizzle caramel topping generously over the cooled cake before serving.