Line a 20cm square baking tin with parchment and oil with groundnut oil.
Stir sugar, lemon juice, and 340ml water over low heat until dissolved.
Boil the mixture without stirring until it reaches 118°C.
Combine cornflour, 570ml cold water, and cream of tartar in a separate pan.
Boil and beat the cornflour mixture until smooth and thick.
Pour the 118°C syrup into the cornflour mixture and stir well.
Simmer on low heat while stirring continuously for one hour.
Stir in the rose syrup, food colouring, and pistachios.
Pour into the tin and allow to set overnight.
Cut into squares and coat in a sifted mixture of icing sugar and cornflour.