Intellectually, she knows that apples turn brown because when you slice them, you open up the cells in the tender white fruit. You make it bleed an enzyme called tyrosinase, which turns the white flesh brown, as it reacts with oxygen.
Willow told her this, when she asked. All nice and polite and happy to be using her big science brain for good, instead of her twitchy magic fingers for evil, though Anya knows Willow doesn't have a clue about evil, not yet. Willow knows about power; she's scraped her skin raw trying to claw off the face she was born with, and let in the rare air outside. She knows how tempting it is, how *special* it is to be able to do things others can't, and she knows she can hurt people, without thinking, but she doesn't know yet. Not about evil. About how much fun it can be to do it on purpose.
Maybe she won't learn, but once you slice them open, it's hard not to stop them from going brown.
Anya knows, practically, that if you put lemon juice on sliced apples, it'll keep them looking pretty, for a while. She can't see how this could apply to Willow. Though she's beginning to relearn the nuance of human analogy, Anya's still picturing Willow slipping naked into a tub full of concentrated RealLemon from the green bottle. She winces when she imagines all the places it would sting -- and winces because she never thought of it herself, back when she was so good at devising vile punishments for cheating husbands. Anya can see, however, that the lemon thing works on the apples, which is enough to make her happy when she's setting them out on the table for a snack.
Heloise told her this, the woman with the silver and black hair in the newspaper who never seems to get any older, no matter how far back Anya checks in the back-issues for these kinds of things, trying to learn to be a real wife, someday soon. There's a thought -- maybe Heloise washes her skin in lemon juice. Maybe that will keep Anya's face from wrinkling and turning brown, as she grows older. It might be worth the wincing.
Or maybe Heloise is just a witch, like Martha Stewart, and the only thing lemons can do for you is make your lips pucker up.
Anya knows this: that Xander likes sliced apples. Likes when she puts them on a tray in the same shape as the apple, as if she just hit it hard on the table like one of those chocolate orange things (he likes those too) and poof! All the little slices fall apart neatly in a circle. She tells him it's not that easy, that she has to spend time on it, cutting them so precisely, and sometimes she slices her finger open when she does it. He nods, and he says thank you, for going to so much trouble, and he kisses her finger, but she's still not sure if he believes her. Anya suspects he thinks all kitchen things happen by magic, unless he has to do them himself, in which case the laws of gravity apply.
Xander told her this, not in so many words, but in the way he smiles at her, wanting to understand, wanting not to have to understand. Wanting to love her enough that it doesn't matter. Anya herself likes to dip the apple slices in caramel sauce, something else Xander told her about. The mild tartness of the apple, the sweet gooey caramel, make the water build up in her mouth just from memory, as she brings the fruit to her lips. She can't see the brown skin, if it's there, when the whole slice is covered with caramel, and it still tastes good. Better than food good -- almost sex good. The lemon, when she can catch the faint sour essence of it on her tongue, on her lips, makes her mouth pucker, but she can live with that.
After all, Xander likes that, too.