First I cut up three red onions and fried them at a medium heat with a drizzle of oil. Just as the onions began to soften and brown I turned down the heat and left them to cook more slowly, stirring occasionally to ensure that all of the onions were evenly cooked. The key to extra tasty onions is the cook them over a long period of time to allow the natural sugars in the onions to caramelise. I usually cook the onions for about 45mins to an hour.
About 10 minutes before the onions are finished cooking, I added a few pinches of sugar to help the caramelising of the onions and also a generous splash of balsamic vinegar to cut through the sweetness. While the onions were just finishing off I greased the ceramic tart dish and prepared the filo pastry (I cheated and bought some pre-made pastry). I used 4 layers of filo pastry with a brushing of water to make sure that the pastry stayed together during cooking. It's important to not have too many layers of pastry otherwise it doesn't cook all the way through and is soggy... it needs to have a nice crispy crunch to serve as a contrast to the soft onions and goats cheese.
I filled the pastry tart with the caramelised onions and layered the goats cheese generously on the top, and popped in all in the oven at 180 degrees for roughly 20 minutes so that the filo wasn't over cooked but so that goats cheese has melted. Then I served the tart with a fresh salad and a drizzle of the balsamic vinegar... et voila! This goats cheese tart easily served four people and was delicious, I thoroughly recommend!
I even had enough filo pastry left over to make some little bite-size cheese and bacon tartlets... I put a dollop of soft cheese in the centre so that they weren't too dry, fried the remaining onions with some chopped up bacon, topped with a little grated cheddar cheese and popped into the oven until the filo pastry is thoroughly cooked... scrumdiddleyumptious!