Although cakey blondies can be a result of either too much liquid in the batter or under-stirring, the most common cause is over-baking. To obtain that soft, chewy texture that blondies are so well-known for, it's important that you bake them only to the point that a toothpick inserted into the center comes out mostly clean, but with a few moist crumbs. If there are no crumbs on the toothpick, your blondies are over-baked.