Same with cakes. Whenever my friends bake a cake, they remove it from the oven when a knife inserted inside comes out clean. I've read this advice many times on

Same with cakes. Whenever my friends bake a cake, they remove it from the oven when a knife inserted inside comes out clean. I've read this advice many times on cooking sites, too. But it's wrong, and the cakes in question are always dry. You should remove the cake from the oven when the knife comes out slightly dirty. The cake will finish cooking outside the oven.