Red Onion Tarte Tatin

Onions are not the most fashionable of the vegetable family and has a bad wrap for creating odors, however in the culinary world onions are the base of many dishes and lend either a savoury or sweet flavour depending on how you cook them. This tart is sweet which is balanced out with the saltiness of the parmesan, comfort food to the extreme. I also recommend you keep a stick of gum for afterwards.
PASTRY:
300g plain flour
150g unsalted butter
50g grated cheddar
1 egg
Pinch of sea salt

FILLING:
1.2 kg red onion
80g unsalted butter
50ml good quality balsamic vinegar
1 teaspoon sea salt
2 bay leaves
Leaves from 4 sprigs of thyme plus extra for garnish
Cracked pepper
100g grated parmesan

METHOD:
Start with the pastry, place the flour, cheddar and salt in large mixing bowl. Cube the butter and add to the dry mixture, rub the butter into the flour till well blended together then add the egg and several tablespoons of cold water and lightly knead together till only just combined. Wrap the pastry in cling film and place in the fridge for 30 minutes to rest.
Grease a fluted flan tin with removable base 30cm in diameter and 3cm deep. Once the pastry has rested roll out on a floured surface till about 4-5mm thick and line the tin with pastry pinch and press down around the edges then refrigerate for a further 30 minutes.
Pre-heat the oven to 200oC, with a folk prick the base of the pastry 10 times and line with grease proof paper and fill with rice or dried legumes, bake in oven for 12 minutes. When the pastry is baked remove the parchment paper and legumes and bake the pastry for another 6 minutes till golden brown.
To make the onion filling peel the onions and slice in half then remove the top and bottom and slice length ways. Put the butter in a large pot and melt over a medium heat till just starting to brown and add the thyme followed by the onion and half a cup of water stir and sweat till the onions have reduce and gone soft. Add the salt, bay leaves and vinegar and simmer for 15 minutes gently stirring from time to time then remove from heat and strain off the excess liquid and remove the bay leaves. Taste the onion and adjust the seasoning with salt and pepper then spoon the onion's into the pastry case and bake in oven at 180oC for 20 minutes.
As soon as the tart is out of the oven evenly sprinkle the parmesan over the onions and leave to cool for 10-15 minutes before slicing. Garnish with fresh thyme leaves and cracked pepper.