Sift the flour and salt on to a workbench. Chop the butter into small pieces and toss in the flour. Make a well in the centre and pour in the water. Work it into a rough heap of buttery lumps, just combined - don't knead it too much. Gather it all together and press it into a disk, sprinkle with a little flour and wrap in cling wrap. Refrigerate for 30 minutes.
For the tart:
Preheat oven to 200 degrees C.
Roll out the pastry, dusting with flour as necessary, and use it to line a 24cm flan tin. Cut out a circle of baking paper that fits in the tart, fill it with beans or lentils, and blind bake it for 20 minutes. Remove from the oven and store the beans for another use. Discard the baking paper. Turn the oven down to 160 degrees C.
Combine the eggs and sugar until well mixed then add the lemon zest and juice. Add the cream and raspberry puree and mix well. Pour into the freshly-baked crust and bake for 30-40 minutes, until almost set. Cool in the tin, at least 30 minutes, then dust with icing sugar and serve.