Preheat oven to 180°C or fan170°C. Grease a 25cm round flan tin. Cut the butter into pieces and rub into the flour to make fine breadcrumbs.

Add the egg yolk and water and mix to make a ball of dough. Wrap in clingfilm and chill for 10 minutes.

Roll out the pastry and line the flan tin. Prick the base with a fork, line with foil and rice or pasta or baking beans and bake for 10 minutes, Remove the foil and it's contents and bake for another 5 minutes.

Meanwhile, gently soften the onions in the oil for 10 minutes, add the sugar and vinegar and cook for another 10 minutes. Add the beetroot and season with freshly ground black pepper.

Mix together the crème fraïche egg and egg yolk in a bowl and stir well.

Pour the egg mixture into the pastry case, top with the beetroot mix and pieces of goat's cheese. Bake for about 25 minutes or until risen and golden. Sprinkle with thyme, if liked, to serve

Takes 55 minutes to cook