Pumpkin pie with red onion and pesto of pistachios

Preparation

• Start by making the dough. This can also be done a (half) day in advance. First put the flour and salt in a bowl. Add the cold butter in cubes and squeeze the butter into the flour until you get a kind of wet sand. Make sure the butter does not get too hot.
• Then add the cold water (preferably water that has been in the fridge for a while). Mix with a ladle, a fork or your hands to a smooth dough. Then sprinkle some flour on your kitchen work surface, place the dough on your work surface and knead it with your hands. Don't knead too much. Shape the dough into a square and wrap in cling film. Place the dough in the fridge for at least 30 minutes.
• Preheat the oven at 220 degrees Celsius (428 degrees Fahrenheit).
• Cut the onion into quarters. Mix the onion in a baking dish with the pumpkin cubes and the 2 tablespoons of balsamic vinegar. Mix well, season the vegetables with salt and pepper and then put the baking dish in the oven. Roast the pumpkin for 10 minutes. Then let it cool, leave the oven on.
• Briefly roast the pistachios in a dry frying pan. Then put the pistachios in the food processor along with the Parmesan cheese, basil and olive oil. Process until you have a firm, quite dry pesto. Taste the pesto and season with salt and pepper if necessary.
• Mix the pesto with the pumpkin cubes. Season the vegetable mix with additional salt and pepper if necessary.
• Butter your quiche tin.
• Remove the dough from the cling film and sprinkle some flour on your work surface. Divide the dough into 2 pieces. Roll out 1 piece of dough with the rolling pin until it is about an inch thick and larger than your quiche tin. Carefully put the dough in the quiche tin and let it hang over the edge. Gently press the bottom and the edges. 
• Put the pumpkin filling in the quiche tin and spread evenly over the tin.
• Now roll out the 2nd piece of dough, also to half a centimetre. Carefully place it on the quiche tin and press the edges of the dough on the edges of the tin. Then cut off the excess dough with a knife. You can use this excess dough to make decorative pieces which you can use to decorate the pie by sticking it on the pie.
• Cut a cross in the top of the quiche with a knife which will allow any steam to escape.
• Beat the egg and brush it on the pumpkin pie. Then bake the pie in the middle of the oven for 40 – 50 minutes. Cover the top with aluminium foil (if it gets too brown) to keep your crust from overbaking. Serve warm or let it cool and serve cold.