The ingredients in this French Onion Tart are simple, but it requires some time to cook the onions. Don’t worry it pays off! Cooking onions slowly, for close to an hour, transforms this kitchen... staple into a sweet almost jam-like star. Making the pastry crust makes a very rich dish, see Chef Tip for a quicker option.
Heat olive oil in a wide skillet over medium heat. Add the onions and cook for 2 minutes, stirring, until they just begin to wilt. Add salt, and cover with a tightly fitting lid or parchment paper. Cook stirring occasionally, until tender and golden brown, about 45 minutes to 1 hour.
Meanwhile, preheat the oven to 375 degrees F. Roll out the pastry dough, if using, until it is about ⅛-inch thick. Bake the crust in the tin with nothing in it for 15 minutes until it is just set and turning golden in some places.
Spread the onions onto the crust, about ¼-inch to the edges. Sprinkle on the thyme leaves. Bake for 15-20 minutes or until the crust is golden.
Making the pastry crust is delicious. When having less time buy a pre-made pizza dough or whole wheat flatbread from your grocery. Pre-bake the crust is not needed if using one of these options.