Hmmm, Gobo, you're a tough one!
Don't like onions but like onion rings? Well, that could be because you haven't had really nice cooked onions, or it could be because you're concentrating on the nice, greasy, tasty outer crust of the rings and ignoring the inside. To me there are few things as wonderful as onions sauteed nice and slow and long on a slow fire -- a good 30 minutes, at least. They're so sweet it's unbelievable. Take those and their butter or oil and mix it in with hot pasta and plenty of freshly-ground pepper and it's just plain nectar.
As for lemon and what it's used with ... well, pasta in this case. A nice tagliatelle maybe, plus plenty of butter or oil, plus the finely-grated zest and the fresh parmesan. Very light, very fresh.
I have to wonder if you (and your girlfriend) have been exposed to really good pasta. It's so amazingly versatile -- can be heavy or light, spicy or not, and takes SO many flavors so well. There must be something in there you'd both like!
I mentioned the Hazans (Marcella and her son, Giuliano) but the book by the son (The Classic Pasta Cookbook) is one you should really consider getting if you want to come up with a variety of nice ways of fixing pasta. It's produced by DK so it's FULL of really enticing photos and is 100% about different ways of making pasta. It's a great book!
Lulu, I'll trade you my (Giuliano's!) lemon pasta for your lemon risotto!! I love risotto, but the only one I eat is my hubby's fabulous chicken one. PM it to me or post it?