It is clear to their fortunate [closed]

"That the best cooks are the first and best critics of their own work is an observation almost trite. It is clear to their fortunate if puzzled guests that the host’s anxious questions about whether the meal would not taste the better for some adjustment are rhetorical." (Jonathan Conlin, Critical Lives-Adam Smith)

I couldn't figure the second sentence out, can you help me?

The adjectival phrase is "fortunate if puzzled". The writer is saying that the guests are puzzled as to why the host/cook is asking whether the meal needs improvement, because the meal is delicious. The writer is also saying that the guests are fortunate, because the meal is delicious. For brevity and style, these two properties of the guests have been combined into the phrase "fortunate if puzzled", which I would write as "fortunate, if puzzled, ".

"It is clear to their guests, who are fortunate, [even] if [they are] puzzled, that the host's questions... are rhetorical."

This explains what a rhetorical question is.