Both Guangzhou and Changsha are famous food cities in China with rich food culture. Here are some possible delicious restaurants:

1. Taotaoju, Liwan District, Guangzhou: Founded in 1885, it is one of the famous time-honored restaurants in Guangzhou, mainly providing Cantonese cuisine and snacks.

2. Juzhou Restaurant in Yuelu District, Changsha City: Founded in 1958, it is one of the famous time-honored restaurants in Changsha, mainly providing Hunan cuisine and snacks.

3. Guangzhou Restaurant in Tianhe District, Guangzhou: Established in 1956, it is one of the famous time-honored restaurants in Guangzhou, mainly providing Cantonese cuisine and snacks.

4. Jinshajiang Restaurant in Tianxin District, Changsha City: Founded in 1984, it is one of the famous time-honored restaurants in Changsha, mainly providing Hunan cuisine and snacks.

5. Nanyuan Restaurant in Yuexiu District, Guangzhou: Founded in 1964, it is one of the famous time-honored restaurants in Guangzhou, mainly providing Cantonese cuisine and snacks.

6. Qin Huang Restaurant in Yuelu District, Changsha City: Founded in 1993, it is one of the famous restaurants in Changsha, mainly engaged in Hunan cuisine and Cantonese cuisine.

In a word, there are many delicious restaurants in Guangzhou and Changsha. You can choose the one that suits you according to your own tastes and needs.