Step 1: Preheat Oven and Prepare Pan : Preheat oven to 350°F (175°C). Line a 9x13-inch baking pan with parchment paper or lightly grease with butter.

Step 2: Make the Blondie Batter : In a large bowl, combine melted butter and brown sugar, mixing until smooth and well combined. Add eggs and vanilla extract, and whisk until fully incorporated. In a separate bowl, whisk together flour, baking powder, salt, and dry cake mix. Gradually fold the dry ingredients into the wet mixture until a smooth batter forms.

Step 3: Add Funfetti :Gently fold in rainbow sprinkles (reserve a few for topping). Add any optional white chocolate chips or nuts if desired.

Step 4: Bake the Blondies : Pour the batter evenly into the prepared baking pan. Sprinkle remaining rainbow sprinkles on top for extra color. Bake in preheated oven for 25–30 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs. Do not overbake — the blondies should remain soft and chewy.

Step 5: Cool and Cut : Allow the blondies to cool completely in the pan. Lift out using the parchment paper and cut into 16 squares with a sharp knife.

Step 6: Serve : Serve as-is, or top with whipped cream, frosting, or a drizzle of melted chocolate for extra indulgence. Perfect for dessert plates, party platters, or lunchbox treats.