This funfetti blondies recipe features deliciously chewy brown sugar and vanilla-laced cake batter-flavored cookie bars. Fun, festive rainbow sprinkles and a creamy vanilla frosting take it over the top!
Preheat the oven to 350F. Line an 8 by 8-inch baking pan with 2 pieces of parchment paper so it hangs over all 4 sides.
Melt the butter in a large bowl in the microwave and let it cool for about 30 seconds to 1 minute. Whisk in the granulated sugar and brown sugar until well-mixed. Whisk in the egg, vanilla extract, and cake batter flavor. Add the flour and salt and stir until combined, being careful not to over-mix. Fold in 4 tablespoons rainbow sprinkles (reserving 1 tablespoon for decorating the top).
Transfer the blondie batter to the prepared pan, spreading it out evenly. Bake until the outside looks light golden, but the inside looks doughy, about 22 to 25 minutes. Let the blondies cool for about 10 minutes in the pan, and then remove them to a wire rack to cool to room temperature.
For the Vanilla Frosting:
While the blondies are cooling, make the frosting.
Add all ingredients to a large bowl. Use a handheld electric mixer to beat until well-combined. You may need to add a bit more heavy whipping cream to achieve the right consistency.
To Frost the Blondies:
Frost the blondies once they’re cooled. Before the frosting sets, top with the remaining 1 tablespoon rainbow sprinkles.
Notes
Don’t Let the Butter Cool Too Much: After you melt the butter, only let it cool for about 30 seconds to 1 minute before whisking in the sugar. This will help make sure you get a gorgeous crackled top!
Cake Batter Flavoring Substitute: If you can’t find cake batter flavor, you can substitute with a combination of butter flavor and almond extract. (About ½ teaspoon butter flavor and ⅛ teaspoon almond extract for this recipe.)
Don’t Overbake: Blondies are done when they still look a touch doughy in the center because they will continue cooking in the pan.
Storage: Once they're cool, wrap blondies well and then store them for up to 4 days at room temperature or up to 1 week in the fridge.
Frosting Optional: Yes, the frosting is delicious and it whips up in just minutes. And yes, it completes the birthday cake look. But it really is gilding the lily; these blondies are amazing even without frosting!