Preheat your oven to 350°F (175°C). Grease and flour an 8x8 inch baking pan or line it with parchment paper, leaving an overhang to easily lift out the blondies later.

In a large bowl, combine the melted butter, brown sugar, and granulated sugar. Mix until well combined.

Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract. The mixture should be smooth and creamy.

In a separate bowl, whisk together the flour and salt. This ensures the salt is evenly distributed throughout the batter.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Be careful not to overmix, as this can result in tough blondies.

Gently fold in the diced apples. Make sure the apples are evenly distributed throughout the batter.

Pour the batter into the prepared pan and spread it evenly. Drizzle the caramel sauce over the top of the batter. Use a knife or skewer to swirl the caramel into the batter. This will create beautiful and delicious caramel pockets in the blondies.

Bake for 30-35 minutes, or until a toothpick inserted into the center comes out with moist crumbs. Be careful not to overbake, as you want the blondies to remain chewy.

Let the blondies cool completely in the pan before cutting into squares. This will prevent them from falling apart.