Preheat your oven to 350°F and line a 9x13 inch baking pan with parchment paper. Melting the butter ahead of time saves you a step since you'll mix it directly into the dry ingredients. I always set my timer for the oven so I don't forget it's preheating.

Whisk together flour, sugar, baking powder, and salt in a large bowl until combined. Pour in your melted butter and mix until the texture looks like wet sand. This creates the base for chewy confetti blondies 4th july sharing bars every single time.

Add both eggs one at a time, stirring well after each addition so everything stays smooth. Stir in the vanilla extract and milk, mixing until you see no flour streaks remaining. The batter should be thick but spreadable at this point.

Fold in the rainbow sprinkles, white chocolate chips, pistachios, and orange zest using a spatula. Be gentle so you don't crush the sprinkles and lose those cheerful colors. My 6-year-old ate three helpings last Tuesday when I accidentally doubled the zest—it was even better.

Spread the batter evenly into your prepared pan and bake for 25-30 minutes until golden. The top should look set but the center will jiggle slightly when you gently shake the pan. Don't skip this check because overbaking turns them rubbery and you'll lose that chewy texture.

Remove from the oven and let these sharing summer dessert bars cool in the pan for 10 minutes. Transfer to a wire rack and cool completely before cutting into 16 squares. I always cut mine while they're still slightly warm so the white chocolate stays gooey.