The peach upside-down cake should be inverted immediately after baking. Once the peaches are taken out of the oven, let them sit for no more than five minutes, as the sugar will harden quickly. Replace any peaches that stick to the pan with the peaches on top of the cake if they stick to it. Once the cake has cooled, let it sit for at least 15 minutes before serving. Served warm, at room temperature, or chilled straight from the fridge, you can enjoy it in three ways.