Ingredients

Step by step

1. Roll out the pastry sheet so that it is slightly larger, then use to line the base and sides of a greased 20cm x 30cm traybake tin. Prick with a fork and chill for 30 minutes. Preheat the oven to 200°C, fan 180°C, gas 6. Line with a sheet of crumpled baking paper and baking beans and bake for 20 minutes. Lightly beat the egg white, remove the paper and beans and brush this over the case to seal. Return to the oven for 6-8 minutes until crisp. Remove and set aside. Reduce the oven to 180°C, fan 160°C, gas 4.
2. Meanwhile, roughly chop 500g of the rhubarb and place in a pan with 50g of the caster sugar and 2 tablespoons of water. Simmer, covered, for 6-8 minutes or until tender. Tip into a sieve set over a bowl to drain, then return the juices to the pan and reduce to about 2 tablespoons of syrup. Stir this back together with the rhubarb and cool.
3. Take the remaining rhubarb and slice on the diagonal into 5cm long chunks. Set aside.
4. For the frangipane, beat the remaining 175g sugar and the butter together until creamy. Mix the ground almonds, flour and salt in another bowl. One at a time, beat the 3 eggs and extra yolk into the sugar and butter, adding a spoonful of the almond mixture after each one. Mix in the lemon zest, extract and the rest of the almond mixture.
5. Spread the cooled rhubarb in the pastry case then smooth on the frangipane. Gently press the rhubarb pieces into the top in a decorative pattern and scatter with the tablespoon of caster sugar and the flaked almonds.
6. Bake for 45-50 minutes, until set. Cool in the tin for 30 minutes before serving, cut into bars.