It’ll be golden brown and puffed in the center. When you press on it, it should feel soft but not liquid-y. You can Insert a toothpick or cake tester into the center of the blondies. If it comes out with a few moist crumbs clinging to it, the blondies are done. If it comes out with raw batter, they need more time. Remember, they will continue to cook slightly and set up as they cool.