The best way to make sure that any cake stays moist is to not overbake it. Keep an eye on it and check by inserting a toothpick into the center. If it comes out clean, the cake is finished baking. Other ways to make sure your cake stays moist is to not overmix the batter and to make sure that your ingredients are at room temperature. If your butter and eggs are too cold, they won’t emulsify properly and oftentimes the butter will leak out rather than bake into the cake.