on bars cool to room temperature. Refrigerate: Cover the lemon bars with plastic wrap or aluminum foil. It's best to keep them in the baking dish if possible. Refrigerate Overnight: Place them in the refrigerator. This not only keeps them fresh but also helps them set further, making them easier to cut and serve. Optional Dusting: If you prefer, you can dust them with powdered sugar before serving, as the sugar can dissolve into the bars if done before refrigeration.