Mix wholemeal and spelt flour in a bowl; coarsely grate in frozen butter. Season with salt; add water and mix until dough comes together.
Grease a 23cm tart tin; line the tin with pastry and chill in the fridge for 15 minutes. for 15 minutes.
Preheat oven to 180 C / Gas 4.
Prick pastry base with a fork; line with a circle of baking paper or foil and fill with baking beans or dry rice. Bake pastry blind for 10 minutes in preheated oven; remove the paper and beans and cook the pastry base for another 5 minutes, or until golden-brown.