Start by mixing the flour, cinnamon, nutmeg, baking powder, baking soda, and salt in a bowl. This ensures the spices and leavening agents are evenly distributed for consistent flavor.
In a large bowl, stir together melted butter, brown sugar, and vanilla. Add eggs one at a time, mixing gently until just combined to avoid overmixing, which keeps the blondies tender.
Gently fold the dry ingredients into the wet mixture until no streaks remain. Toss chopped apples with a little cinnamon and fold them in carefully, ensuring even distribution without overmixing.
Spread the batter evenly in a lined 8×8-inch pan. Bake at 350°F (175°C) for 40 minutes, or until a toothpick inserted in the center comes out clean with a few moist crumbs.
While the blondies bake, toast pecans on a rimmed baking sheet for 4-7 minutes, stirring halfway through. This enhances their nutty aroma and flavor.
Once the blondies have cooled, drizzle or spread the caramel sauce over the top. Sprinkle toasted pecans for extra crunch and visual appeal. Let it set slightly before slicing.