Quiche

Buy a ready-made pie crust.
Left-hand picture: Saute onions in a skillet with olive oil until translucent. Mix with grated cheese (we used a Gruyere from Wisconsin that was really not good on its own but quite tasty once cooked), heavy cream, salt & pepper and pour into the crust. I added a couple of tomatoes on top for the looks of it. Eat warm or cold.
Right-hand picture: Really you can put anything you want in there, a great 'left-overs' dish. Here I mixed steamed asparagus cut in chunks with 3 egg, some cream, and left-over cheeses (a goat cheese and a blue cheese) and decorated with the top pieces of the asparagus.
Cook in the oven at 350 F / 175 C until the surface starts to brown (~30-40 minutes).