Make the pastry. Set the oven at 200C/gas mark 6. Reduce the flour and butter to coarse crumbs in a food processor, then add the egg yolk and a few drops of water and bring together to form a ball. Wrap in greaseproof paper and chill for 30 minutes.
Put the salmon in a roasting dish, trickle with oil and season with salt, pepper and half the dill. (I often wrap the salmon in foil to make cleaning the dish easier.) Bake for 15-20 minutes until lightly cooked. Remove and leave to cool.
Roll the pastry and use it to line a 22cm loose-bottomed tart tin. Make sure there are no tears or cracks. Fill the pastry case with greaseproof paper and baking beans and bake for 25 minutes.
Remove the baking beans and foil and return the pastry to the oven for 5 minutes until dry to the touch. Remove the tart case and lower the heat to 180C/gas mark 4.
Beat together the eggs and cream until lightly mixed, then season with salt and pepper. Finely slice and add the spring onions. Break the salmon into large flakes and place in the pastry case.
Add the remaining dill, then the cream cheese in tablespoon-sized pieces. Pour in the egg and cream mixture, then slide back into the oven on top of the heated tray and bake for 25 minutes.
The tart is ready when lightly set. It should be wobbly when you gently shake the tray. Remove from the oven and leave to cool before cutting.