Preheat your oven to 350°F and line an 8x8-inch baking pan with parchment paper. Melt the butter in a small saucepan over low heat, then let it cool for about 2 minutes. You want it warm but not hot before mixing with the rest.

In a medium bowl, whisk together the flour, baking powder, and salt. Set this dry mixture aside—don't skip this step because it helps distribute the leavening evenly.

Pour the melted butter into a larger bowl, then add the sugar and stir until combined. Add both eggs one at a time, stirring well after each addition. Mix in the milk, vanilla powder, and lemon zest until everything looks smooth.

Gently fold the dry ingredients into the wet mixture using a spatula. Don't overmix or your confetti blondies family 4th july will turn out tough instead of tender. Fold in the white chocolate chips and about three-quarters of your sprinkles, saving some for the top.

Pour the batter into your prepared pan and spread it evenly with a spatula. Sprinkle the remaining rainbow sprinkles across the top, pressing them down gently so they don't fall off during baking.

Bake for 28 to 32 minutes—the tops should look golden but still slightly soft in the center when you jiggle the pan. I always check mine at minute 28 because ovens vary, and these are best when they're a little chewy in the middle.

Cool the confetti blondies family 4th july in the pan for at least 15 minutes before cutting into 12 squares. If you try to cut them too early, they'll fall apart, so patience here really pays off.