I have taken a cooking class!
In which borough?
No THAT was in guadalajara.
Is this usage of "that" correct? What does it mean?
I have taken a cooking class!
In which borough?
No THAT was in guadalajara.
Is this usage of "that" correct? What does it mean?
An emphatic demonstrative pronoun, "No, that is|was ..." is often used when a person you are speaking with has gotten something wrong. The pronoun refers back to what was just mentioned by them, not by you.
Remember the time we played hooky when we were in Mr. Johnson's algebra class?
-- No, that was in Mr. Smith's geometry class. We were in geometry together, not algebra.
I've signed up for a cooking class!
-- The baking class you told me about a few weeks ago?
No, that was full up. This one is about Icelandic offal dishes and had plenty of openings. I'm doing it mainly to meet new people.
I think "it" would fit better, but it is understandable.
In which borough?
This question asks where the class was held. The speaker is presuming it was a class taken locally, so is asking in which district of the city the class was held. If it was New York, then the answer might be "Queens". If it was Toronto, some years ago (pre-amalgamation), the answer might be "Scarborough".
No, that was in Guadalajara.
The response is "that" (the act of taking the class) was in Guadalajara (an entirely different city, and probably a different country).
A: I have taken a cooking class!
B: In which borough?
A: No, THAT was in Guadalajara.
B's question was about the place of the cooking class.
When A used THAT, it's understood to be referring to the place (in Guadalajara).
A used capital letters THAT for emphasis as B might have assumed the place to be somewhere local.
Different meanings of "that".
OP's conversation:
I have taken a cooking class!
"In which borough?".
"No. THAT was in guadalajara."
If the dialogue was a single sentence:
I have taken a cooking class that was in Guadalajara.
Here "that" is a relative pronoun which introduces the restrictive relative clause (identifying the noun "cooking class").
Meaning of "that" in the dialogue.
The listener thought that the class was held in the US. (Which borough?).
If the location was in New York, the speaker's reply would have been,
"This was in New York."
The speaker clarifies that it was held in Guadalajara, Mexico by saying,
"No, that was in Guadalajara."
"That" in the sentence is a demonstrative adjective emphasizing that the cooking class was held in another country.
In a similar way, "that" can also mean something which happened in distant past