You can buy moon cakes from Hefei Hongding Restaurant through Meituan app. The specific steps are as follows:

1. Open Meituan app and enter the home page.

2. Find the door-to-door pickup on the homepage and click Enter.

3. Search the name of the moon cake in Hefei Hongding Restaurant in the search bar, and click Place an Order.

It should be noted that the above purchase methods may change with time. Please refer to the actual situation.