Maybe BU's calling range is wider than what his stats over 60 hands suggest, still i don't think he ever just flats Asxs in that position, so we're looking at 22-99 and some random OESD, pair+OESD, non-nut flush+GS or other combos draws.
You have ~15 outs against a pair+OESD, pair+GS or an overpair like 99, you have any other flushdraw crushed (he's unlikely to have the As, if he does and the money goes in too bad really :\), 9 outs against a set.
If you 3bet/call on the flop you're up against sets mostly, and maybe something like 7s6s. You stack that last hand by calling on the flop if the flush hits on a turn anyway. Not that bad but not good either.
If you call and a spade hits you'll likely get another bet out of him, your hand could also be an overpair so he will bet again on the turn or call a bet on the river. Some people will still stack off with a set on a spade turn because you could have something like AsAx with a redraw.
All in all, i'd also call the raise and see what happens on the turn.
On a blank if he bets strong again i'm folding, on a spade obviously we stack off.
Worse case scenario decision-wise would probably be something like a J turn and him betting huge into us again after we check. Still i would probably fold because his range for following through on a "blank" turn is a lot stronger than his flop raising range and the J doesn't really help us against that range. Plus with only one card left to come our equity isn't as good as it was on the flop.