This caramelized red onion tart will easily become a favorite stand-by recipe. It is the one you can call on when you want to cook something quick, tasty and with a wow factor. The tart is incredibly versatile serve it as individual tarts, or make a large one. It is delicious warm or cold and makes a great lunch box, picnic or buffet treat. You can dress the recipe up or down (see the variations below). The onion tart is also a great dish for vegetarians, perfect served as a starter or with a salad or seasonal vegetables makes a great main course as well.