Combine the butter, sugar and salt. Mix in the flour and water, mix quickly to create a soft dough, cover and chill for approx. 30 mins. Roll out the dough into a circle (approx. 32 cm in diameter) between two sheets of baking paper, remove the upper sheet of baking paper. Place the dough in the tin along with the bottom sheet of baking paper, chill for approx. 30 mins.
Mix the butter, flour, almonds and sugar. Arrange the plums on top of the pastry base. Rub the crumble mixture over the top by hand.
Approx. 50 mins. in the lower half of an oven preheated to 180°C. Remove from the oven, allow to cool slightly, then remove from the tin and leave to cool completely.