Translation:It says to add salt and pepper to taste.
What would "It says add salt and pepper to taste" mean? I would understand if it said, "It says add salt and pepper FOR taste", but to taste? Is this a mistake in duolingo's translation or is this some kind of cooking jargon I don't understand
It is a recipe phrase. I see 'Add salt and pepper to taste' all the time. :)
I'd say the latter. It means to add as much salt and pepper as is your taste; if you don't like pepper you can leave it out, if you like spicy food you can put in a lot, and so on. Check out http://www.thekitchn.com/food-science-salting-to-taste-49868
The most common way to express the thought in Italian recipes is "quanto basta", or simply q.b. (as much as needed).
I just listened to a standup comedian who said "Undress to your comfort level". Similar use. Perhaps it would make more sense to you if it said "to your taste" ?