Preheat the oven to 200C/400F/Gas 6.
Place the beetroot onto a tray with the garlic, thyme and 50g/2oz of the sugar and roast in the oven for 1-1 ½ hours, or until tender. Once cooked allow the beetroot to cool before peeling.
Cut into very thin slices on a mandolin, or use a very sharp knife.
Roll the pastry out to a rectangle the thickness of pound coin and prick with a fork. Place onto a flat baking sheet and cover with a second tray to stop the pastry rising.
Bake in the oven for 15-20 minutes or until the pastry is golden-brown.
Heat the butter in a small saucepan and fry the onions for 3-4 minutes, or until just softened.
Add the port and red wine vinegar and cook until reduced by half in volume. Blend the mixture in a food processor until smooth.
Meanwhile, heat the remaining sugar in a small saucepan with two tablespoons of water. Once the sugar has dissolved, increase the temperature so that the mixture browns and caremalises. Once the mixture is dark brown in colour, remove the saucepan from the heat and add 20ml/¾fl oz water to stop the caramel from setting hard.
Allow the caramel to cool slightly, then add the salt and sherry vinegar.
Spread the red onion purée over the cooked pastry, then lay the beetroot on top in a fish scale pattern.
Drizzle with the caramel and place in the oven for 2-3 minutes, or until hot.
Meanwhile for the salad, whisk the sherry vinegar and olive oil until well combined and coat the herbs with the dressing.
Remove the pastry from the oven, trim the ends and cut into triangle shapes.
To serve, place a scoop of goats’ curd on top of the tart. .Sprinkle over the pine nuts and drizzle generously with the caramel. Serve alongside the herb salad.