1. Preheat oven to 180 degrees (fan) and place a baking sheet inside to heat up. Lightly grease a pie dish with a little butter.

2. To make the pastry by hand, place the flour in a mixing bowl. Rub in the butter until the mixture resembles breadcrumbs. Mix in the sugar. Use a knife to work in the egg, then bring together to form a dough (add a drop of water if required). Wrap the pastry and refrigerate for 20 minutes (to make pastry in a food processor, simply blitz the flour, butter and sugar to fine breadcrumbs, then work in the egg to form a dough).

3. While the pastry is resting, put the rhubarb into a medium-sized heavy-based saucepan with the sugar and the lemon zest and juice. Cook over a medium-high heat for five minutes, then cover and reduce the heat, cooking for another five minutes or so, until the rhubarb is just tender but still retains its shape. Allow to cool.

4. Divide the pastry into a large and small piece. Roll out the larger piece (about 225g) and use it to line the base of the pie dish. Trim away any overhanging pastry, then brush the pastry rim with egg glaze.

5. Spoon the cooled rhubarb into the pie base, discarding any excess liquid. Roll out the remaining pastry to cover the filling. Trim away overhanging pastry. Seal the pastry edges together either by firmly pressing your thumb around the rim of the dish, or crimp using the back of a fork. Score two slits in the centre of the pie (for the steam to escape).

6. Before baking, brush the entire lid with egg glaze, then lightly dredge the top with extra sugar.

7. Bake on the hot baking sheet in the preheated oven for 30-35 minutes or until the top is golden and the rhubarb starts to bubble up through the middle (turn the oven down if the crust is darkening). Serve warm, with ice cream or freshly whipped cream.