Dice butter into small cubes and put in freezer for at least 30 minutes. Add an ice cube to a cup of cold water.
Add flour, sugar, salt, and baking powder (for savory) to a food processor and pulse a few times to combine. Add cold butter cubes and pulse around 10 times until it resembles yellow cornmeal mixed with bean-sized bits of butter. Remove the cover and blade and transfer to a medium sized bowl.
Slowly mix in ice water and sour cream (for flaky) or white wine, egg yolks, and lemon zest (for savory) and bring together with your hands. Remove from the bowl to a lightly floured work surface. Knead the dough into a ball. Cut ball in half, and wrap each half tightly in plastic wrap. Place in refrigerator to chill for 1 hour or more. If not using both halves, put other in a sealed freezer bag and place in freezer.
Transfer 1 unwrapped half of chilled dough to a lightly floured work surface. Roll into a circle 11-inches across and ¼ to ⅓-inch thick. Place in pie plate and crimp edges all the way around. Place in refrigerator until ready to fill and bake. If using a crust on top, do the same thing and lay over the pie filling and either crimp the edges together or cut into strips to be laced.
Preheat oven to 375℉ (190℃). Once heated, place pie in oven and bake for 20 minutes. After 20 minutes, reduce heat to 350℉ (175℃) and bake until golden brown, about 45 to 50 minutes. If it seems be be on the verger of burning, place foil around the edges.