This tart is good served either warm or at room temperature. It's great for picnics, as it is easy to eat with your fingers.
250g/8oz plain flour
A pinch of salt
100g/31/2oz cold unsalted butter, cut into cubes
For the topping
1 large bunch of Swiss chard, destalked
20 little tomatoes, roasted in the oven until the skins have just burst
5 tbsp crème fraîche
100g/31/2oz grated Parmesan cheese
50ml/2fl oz extra-virgin olive oil
Sea salt and freshly ground black pepper
Place the flour, salt and butter into a food processor and pulse until it is the texture of sand. Add a little water and blend until crumbly. Remove and place on a floured surface, and knead the dough until it forms a cohesive ball, then rest in the fridge for an hour until firm. Meanwhile, blanch the chard: immerse it in boiling water for 2 minutes, refresh it in iced water and then drain well.
Heat the oven to 200C/400F/Gas6 and flour a large flat baking tray. Roll out the pastry on top of the baking tray until it covers the tray evenly – it should be fairly thin (no thicker than an eighth of an inch). Prick the base well with a fork. Cover the pastry with a baking tray of the same size, so essentially the pastry is lying in the middle.
Place in the oven and bake for 20 minutes; the pastry should be almost cooked and beginning to brown. Remove from the oven and allow to cool slightly for five minutes or so. Scatter the chard and roasted tomatoes over the base, season with salt and pepper, spoon over the crème fraîche and scatter over the Parmesan. Return to the oven and cook for a final 10 minutes. Drizzle over the olive oil as the tart comes out of the oven and allow to cool for a few minutes before slicing.