Flaky Rye Pie Dough

75 g / v. scant 2/3 cup rye flour
175g / 1 1/2 cups unbleached all-purpose flour
1/4 teaspoon fine grain sea salt
8 oz / 1 cup salted butter
1/4 - 1/3 cup / 60 - 80 ml cold water or beer

Maple Buttermilk Filling

zest of one lemon
2 tablespoons brown sugar
6 egg yolks
1/4 cup flour
2/3 cup maple syrup (pref. grade b)
2 cups buttermilk
1 teaspoon vanilla extract
scant 1/2 teaspoon fine grain sea salt

Large grain sugar, for sprinkling