Preheat your oven to 350°F and line a 9x13-inch baking pan with parchment paper. Melt the butter and stir in the sugar until combined — you don't need to beat it, just mix it together until it looks kinda crumbly. This takes about 2 minutes and makes the batter come together super easily.

Crack both eggs into the butter-sugar mixture and add the alcohol-free vanilla extract. Whisk these together for about 1 minute until the eggs are fully incorporated and the mixture looks lighter. Don't overmix — just until you don't see streaks of egg white anymore.

In a separate small bowl, whisk together the flour, baking powder, salt, and lemon zest. This step ensures your confetti blondies 4th july bake evenly without any pockets of baking powder. Pour the dry ingredients into the wet mixture and fold gently with a spatula until just combined, about 8-10 folds.

Stir in the milk until the batter smooths out and becomes spreadable. The batter should look thick but pourable — not liquidy. If it looks too thick, add another tablespoon of milk (yes, I've done this before and it saves dry bars).

Fold in the white chocolate chips and then gently stir in the rainbow sprinkles last. I always add sprinkles at the very end because if you mix them too much, they start bleeding color into the batter (which honestly looks kinda muddy). Spread the batter evenly into your prepared pan using an offset spatula or the back of a spoon.

Bake for 25-30 minutes until the top is golden brown and a toothpick inserted in the center comes out with just a few moist crumbs. Don't panic if it looks slightly underbaked — these bars actually firm up beautifully as they cool. I learned this the hard way my first time making funfetti summer bars.

Let the pan cool completely on a wire rack for at least 1 hour before cutting into 16 squares. Cutting while they're warm will result in crumbly pieces, so patience here really pays off. Once cooled, you can store them or serve them immediately with whatever toppings you'd like.