[Because there are ~*~two kinds of people in the world~*~, and guess which one Ciel is in relation to Sebastian? Anime!Sebastian stares mournfully out a window. He uncovers the tray, serves the cake slice and pours the tea with the usual flourish, yada yada.]
If that pleases the young master. [He could say something sassy about how those pastries were bought with Sebastian's hard-earned money, you little freeloader, but... altered memories or not: everything Sebastian owns belongs to Ciel, and frankly he's kind of offended at AU!himself for failing to remember this. And at him being okay with having Ciel eat mediocre tavern food (it's possible Sebastian has been making extra extra scrumptious food these last few days to balance things out a little). Non-sassy, - but probably still obnoxiously - deferential answer it is.]
...Ah, just a moment, please. [He kneels to fix that crooked tie. Such gentle movements, oh my.]