Roast rhubarb with pistachio cake

Method

1. For the rhubarb, heat the oven to 110°C/fan90°C/gas ¼. Wipe the rhubarb stalks clean, trim off the ends and cut into 5cm long pieces. Peel 3 wide strips of zest from the orange and cut them across into pine needle-like shreds, then squeeze the juice from the orange.
2. Arrange the rhubarb pieces in large shallow roasting tray and scatter over the orange zest and sugar. Squeeze over the orange juice. Cover the tin tightly with foil and bake for 1½ hours. Remove from the oven, uncover and carefully pour the released juices into a pan. Boil rapidly for 5-6 minutes until slightly reduced. Cool, then pour back over the rhubarb. Chill if you wish.
3. For the cake, turn up the oven to 160°C/fan140°C/gas 3. Put the pistachios into a pan of boiling water and simmer for 8 minutes. Drain, then wrap in a clean tea towel and rub to loosen the skins. Remove the nuts, picking off any stubborn pieces of skin. Spread on a baking tray and bake for 10-12 minutes until dry but not browned. Cool, then grind in a food processor until quite fine. Add the flour and baking powder and grind to an even finer mixture. Stir in the ground almonds.
4. Grease and line a 23cm loosebottomed cake tin with non-stick baking paper. Put the eggs and sugar in a large bowl and whisk with an electric mixer for 5-7 minutes until thick and moussey. Whisk in the orange zest and rosewater. Reduce the speed and slowly drizzle in the oil, then the melted butter, around the edge of the mixture, waiting for each addition to be mixed in before adding the next. Retain as much volume as you can in the mix.
5. Gently fold in the ground pistachio mixture with a metal spoon, then pour into the prepared tin and lightly level the top. Bake for 50 minutes or until a skewer pushed into the middle comes out clean. Leave to cool in the tin for 10 minutes, then remove and leave to cool on a wire rack if you wish (see introduction). Dust lightly with icing sugar, cut into slices and serve with the rhubarb and scoops of pistachio ice cream.