We've read how professional bakers occasionally moisten cake layers with simple syrup, especially if the cake will be sitting out for a long period of time or needs to be baked in advance (as with wedding cakes).
So, we mixed a couple of tablespoons of raspberry jam with just enough hot water to dissolve the jam and make it runny. When the cake came out of the oven, we poked small holes all over the top with a toothpick and poured the jam syrup over the cake while it was still in the pan, spreading out the syrup with a spatula until it soaked in.
Now, a few things we need to point out. This was a moist cake to begin with, so the finished product was quite spongy and stuck to our fingers when we touched it. Since we were just icing that one layer and didn't need it to be particularly level, we just inverted it onto a plate once it cooled, then iced it. If you're making a layer cake and need to handle the layers or trim them with a serrated knife, you may want to do that before you pour over the jam syrup. The syrup should still soak in easily, maybe not quite as easily as over a warm, just-out-of-the-oven cake, but the hot water will help.
Raspberry and chocolate was a tasty combination, but we think apricot jam syrup over a yellow cake would be amazing. This would also be a good way to liven up a cake that's been frozen or just sitting in the refrigerator for a few days.
(Images: Elizabeth Passarella)