9 max SnG 0.5$ hands A9s postflop oop against a TAG

To not cbet was a mistake according to our equity against his preflop range

Call and reevaluate OTT is also reasonable coz I doubt a good hand would have bet on bigger size on such dry flop
I would put him on something like this after his donk bet

I don’t think it’s a too bad of a play to check fold the flop against a nit, but I would cBet here as well with middle pair.
I wouldn’t be surprised if his defending range is even tighter than you suggested and he most likely 3bet AA or KK as well pre-flop.
Also I wouldn’t mind to fold A9s right away. I expect there is a decent change you will play the hand often multi way if you raise here.

Cheers,
SDK1987

in a SnG with 7 players you should be opening UTG very tight, A9s is a definite fold, even AJ might be a fold too