Mix the flour, butter, salt, and cardamom. Add water and mix until it becomes a ball. Be sure not to overmix.
Preheat the oven to 350 degrees F.
Flour surface and rolling pin to roll pastry out on. Roll to about 1/4-inch. Place in a 9-inch pie dish and crimp the edges. Line crust with foil to maintain shape. Bake at 350-degrees for about 20 minutes. Remove foil and continue baking for another 5 minutes. Remove and let cool.
To make the Salmonberry filling: Crush 2 cups of the Salmonberries through a sieve. This will take some time but it is essential to remove all of the seeds. Add water to Salmonberry juice to make 1 1/2 cups of liquid. Put the juice and water into a pan. Add sugar and salt.
Mix the cornstarch and cardamom with some of the juice, then add it to the sieved berry mixture. Cook on medium heat, stirring constantly for about 5 to10 minutes. Do not scorch. Remove from heat and let cool. Add remaining berries, stir and pour into the pre-baked shell. Chill pie until completely cold.
Whip cream until stiff peaks form. Pipe or spread over the top of the pie and serve.