Maple Buttermilk Pie

INGREDIENTS

• 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
• 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