Again, these are best and have the perfect lava when baked fresh. However, if you baked them ahead or have leftover/frozen cakes, they can be reheated. From the fridge, cover the cake with a damp paper towel and microwave until it is warm and the center is still soft. Do NOT over-microwave or the lava in the middle will cook through. In my microwave, it takes about 30 seconds. From frozen, make sure to thaw the cakes fully overnight in the fridge before microwaving.