1. Preheat your oven to 350°F (175°C) and line a 9×13-inch baking pan with parchment paper, allowing the paper to hang over the edges for easy removal.
2. In a large mixing bowl, combine the melted butter, brown sugar, and granulated sugar. Whisk until smooth, then add in the eggs and vanilla extract, mixing until well combined.
3. In a separate bowl, whisk together the flour, baking powder, salt, cinnamon, and nutmeg. Gradually add the dry ingredients to the wet ingredients, stirring just until combined.
4. Fold in the diced apples gently. Pour the batter into the prepared baking pan, spreading it out evenly with a spatula.
5. Drizzle the salted caramel sauce over the top of the batter, then use a knife to swirl it gently into the batter.
6. Bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean. Keep an eye on the blondies as they bake, as the caramel can cause them to brown quickly.
7. Once baked, sprinkle the top with coarse sea salt while still warm. Allow the blondies to cool completely in the pan before lifting them out using the parchment paper.
8. Cut into squares and drizzle with additional caramel sauce if desired before serving.

One of my favorite tips is to let the blondies cool overnight. This gives the flavors time to meld beautifully, and they’re even more delicious the next day!