Because the ricotta cheese keeps the cake moist, you can easily store it in a tightly sealed container on the counter. It will keep for a day or two at room temperature. Store the cake in the refrigerator for four or five days to make it last a little longer. It's excellent served chilled! You may also keep the leftover cake in the freezer. Just be sure it is completely cooled and stored in an airtight container. In the freezer, lemon ricotta cake will last for about two months.