½ cup sugar
4 tbsp. butter
2 tbsp. water
2 tbsp. white wine vinegar
8–10 red onions, halved horizontally
250g readymade puff pastry
1 egg yolk, beaten
3 sprigs of thyme
Preheat the oven to 200°C.
Melt together the sugar, butter, water and vinegar in a Le Creuset Tarte Tatin pan. Bring to a boil and cook until it is a deep caramel colour.
Arrange the onion halves along the base of the pan.
Cover the layer of caramelised onions with the puff pastry, tucking the edges in underneath the onions.
Brush the pastry with the egg yolk, and bake for 25–30 minutes or until the pastry is golden brown.
Remove from the oven and flip the Tarte Tatin over onto a serving plate. Garnish with thyme sprigs and serve warm.