Actually, in hindsight, even though it means the same thing in English, the German doesn't include "kommt aus". Instead it says "sind aus". So if Duolingo is stuck on literal translations it wouldn't be accepted. However, Duolingo does frequently accept other translations that aren't necessarily literal, so I still think that it should be accepted.
I'd say that a main ingredient of a Torte is cream, while a Kuchen is more often just dough, perhaps with fruit in or on it.
So an "apple pie" would be an Apfelkuchen, I'd say, and there's no one German word that quite corresponds to "pie".
But a cheesecake can also be a Käsekuchen - a Käse-Sahne-Torte "cheese and cream cake" is something slightly different, I think, but similar. Try doing a Google Images search for the two terms.
I agree. Thinking about it, it also seems to me that a Kuchen – if it isn’t all dough like with Marmorkuchen – often still has the dough wrap up at the sides (but not completely around as is the case with the prototypical pie). It is also fairly variable in overall form. It many are round disks but there are other forms as well. Some more common shapes are that of a doughnut, a loaf of bread, half of a sphere or simply rectangular to fit the shape of your standard kitchen baking tray. Torten on the other hand are pretty much always disks/cylinders.
Also, a Kuchen is always baked, whereas with a Torte, you often pre-bake the dough parts and then assemble the whole thing afterward (usually this involves putting differend layers of ingredients on top of each other). As a result, Torte is pretty much always room temperature at most, often cooler (cream doesn’t stay in place if you heat it, and there are even more heat-sensitive variants as well, for example Eistorten “ice cream tarts”). I’m not an expert though; there may well be Torten which are baked as a whole as well
Küche with an Umlaut ü means kitchen. Kuchen, with no Umlaut and as a consequence of that a different pronunciation of ch, means cake. Note also that Küche is feminine and has no -n in the singular. Kuchen is masculine and has an -n in the singular (so you can only tell whether it’s singular or plural from the article: der Kuchen = singular; die Kuchen = plural).