700 g (4 cups or 1 1/2 lbs) rhubarb cleaned and cut into slices
200 g (1 cup) sugar (or more according to how sour the rhubarb is)
1/2 teaspoon cinnamon
3 tablespoons cornstarch
45 ml (3 tablespoons) lemon juice
125 g (1/2 cup) raspberries
InstructionsMix 3 cups rhubarb, 1 cup sugar, and cinnamon and cook over moderate heat, stirring constantly, until sugar is melted, 5 to 6 minutes. Mix cornstarch and lemon juice in a cup. Add the cornstarch mixture to the rhubarb mixture and boil, stirring constantly, until rhubarb is thickened, about 5 minutes, and transfer mixture to a bowl. Cool mixture to room temperature, about 30 minutes.Carefully fold in the raspberries and the remaining cup of rhubarb into the cooked mixture until just combined. Chill the rhubarb filling, covered, at least 30 minutes, or until cold. Transfer to prepared pie shell and bake as normal. This filling is also excellent over a layer of frangipane.