I think it's Brasil Open, in Bahia / Brasil. The big problem is that it's after the US Open, so the field will be usually poor, because all the great players will be tired after all the hard American season. The prize money is even bigger to attract more players.
The website sucks 'cause it's only in Portuguese and there are very few photos from the tournament, etc..
BUT.... the place is amazing. It's the biggest Brazilian resort, with everything a tennis player or any person would desire. Beaches, hot climate, tennis courts, golf fields, great Hotels (Marriot, Sofitel, Renassance (?), etc etc etc) And for me, it's the best one because it's very close to my home and I can always attend it.