The expression בהזמנה הזאת is unusual and idiomatic and, for us, unclear.
Rashi, with many sources, (for example, the Sh'iltos,) says that the Gemara's advice is that one should not get used to eating meat often, because doing so creates an appetite that will demand satisfaction, and meat is expensive. אלא בהזמנה הזאת - כאילו הוא צד שאינה מזומנת לו כלומר לא יאכל בשר תדיר שלא יעני:
The Kli Chemda (Breishis 27:3) says the following:
A choshuveh correspondent directs me to the Eretz Chemda (see the following page as well) (from the Malbim), who discusses and brings mekoros for the Rambam. Thank you.