Red onions and beetroots go well together and this buttery upside down tart brings out the rich, sweet flavours of both. This recipe is by The Hairy Bikers. I use shop-bought puff pastry which I cut just a little larger than the size of the dish in which the tart will bake. I chill that in the fridge whilst I make the filling.
First, I roast 400g of washed, trimmed but unpeeled beetroot cut into wedges and wrapped completely in foil on a baking tray. Usually, this takes around one hour. I then set them aside and let them cool. Sometimes, I do this the day before and keep them in the fridge.
When I am ready to make the tart, I melt 30 g of butter in a frying pan, slice two red onions into thin wedges and cook them in the butter at low to medium temperature until they are softened. Then I turn up the heat and add 1 tablespoon of soft brown sugar and 1 tablespoon of sherry vinegar, stirring it all until the sugar turns into a sticky, buttery caramel.
Then I sprinkle some thyme (leaves of one sprig) and add the already cooked beetroots and some salt and pepper, mixing well to coat everything in the sauce. I then transfer the beetroots and onions from the pan into an oven-proof dish. I leave to cool to room temperature before I add the pastry on top, tucking it into the dish to curl around the beetroot and onion filling.
I bake this at 180°C (fan oven, 200°C if not) for around 25 minutes, or until the pastry is puffed up and golden brown in colour. I take it out of the oven and leave it for 10 minutes before turning it out onto a serving plate, filling now side up. I sprinkle a little more thyme leaves and some crumbly goat's cheese for a creamy addition - or Feta for a milder taste.
This makes a tart large enough for four slices. A green salad and coleslaw are the ideal partners to this sweet and flavourful seasonal tart.