Torta della Nonna can be made a day or two in advance, as it tastes even better once it has had time to chill and the flavors meld together. After baking, let the tart cool completely, then refrigerate it for at least 2 hours before serving. It should be stored in the refrigerator, covered with plastic wrap or in an airtight container, to prevent it from drying out. It will stay fresh for up to 3-4 days. Dust it with powdered sugar just before serving for the best presentation.