roll out 1 crust and line a pie pan with it
fill with chopped rhubarb, then dot with the butter
mix flour, sugar, zest, pinch of salt together in bowl
beat eggs together and stir into the flour sugar mixture
pour evenly over the chopped rhubarb and butter
put pie pan in fridge to chill until the top crust is ready
pre-heat oven to 450˚
roll out top crust and place over the pie, seal edges with water, pinch to seal and trim edges
you can make a lattice crust if you prefer
brush crust with egg yolk beaten with water
bake at 450˚ for 15 minutes
then reduce heat to 350˚ and bake another 25-30 minutes