To make the pastry, tip the flour and butter into a bowl, then rub together with your fingertips until completely mixed and crumbly. Add 8 tbsp cold water, then bring everything together with your hands until just combined. Roll into a ball and use straight away or chill for up to 2 days. The pastry can also be frozen for up to a month.
Roll out the pastry on a lightly floured surface to a round about 5cm larger than a 25cm tin. Use your rolling pin to lift it up, then drape over the tart case so there is an overhang of pastry on the sides. Using a small ball of pastry scraps, push the pastry into the corners of the tin. Chill in the fridge or freezer for 20 mins.
Heat oven to 200°C/fan 180°C/gas 6. While the pastry is chilling, heat the butter in a pan and cook the onions for 20 mins, stirring occasionally, until they become sticky and golden. Remove from the heat.
Lightly prick the base of the tart with a fork, line the tart case with a large circle of greaseproof paper or foil, then fill with baking beans. Blind-bake the tart for 20 mins, remove the paper and beans, then continue to cook for 5-10 mins until biscuit brown.
Meanwhile, beat the eggs in a bowl, then gradually add the cream. Stir in the onions and half the cheese, then season with salt and pepper and your chosen Tabasco® sauce. Carefully tip the filling into the case, sprinkle with the rest of the cheese, then bake for 20-25 mins until set and golden. Leave to cool in the case, trim the edges of the pastry, then remove and serve in slices.Recipe courtesy of Tabasco®