Preheat oven to 200°C (400°F)
Cut the rhubarb into 1 cm rounds
Pour over sugar, potato flour and cinnamon
Butter a pie form and pour in the pie filling
Mix all dry ingredients separately
Add softened butter and mix together
Grate the almond paste over the rhubarb and then pour the crisp mix evenly over the pie
Bake for 20 min in the oven