Buttermilk Cardamom Slab Pie

I brought this to an early Thanksgiving dinner, and boy did I love it.  Simple, not nearly as dramatic as other recipes in Pie Squared, but really very good.  I took the leftovers to work and people were very impressed.
This is a slab pie, which is made in a 1/4 sheet pan (or a 9" x 13" pan would probably work).  

Filling:

8 Tbs. butter
1 c. (200 g) sugar
3 eggs
1 egg yolk
1 c. buttermilk
1 Tbs. lemon juice
1 tsp. vanilla extract
1/4 tsp. ground cardamom


Butter Crust:

1 1/2 c. (160 gm) all purpose flour
8 Tbs. (113 gm) cubed butter
dash of salt if using unsalted butter
1/4 c. (60 ml) ice water

For the crust:
Ideally, weigh the ingredients.  Put the food processor bowl on the scale and weigh the flour, then the butter.  Use the blade and pulse about 15 or so times to cut the butter into the flour, leaving the butter in pea sized pieces.  Add the ice water all at once, and pulse until dough comes together, just barely.  Lay out a piece of plastic wrap and dump dough onto it.  Try not not handle it, using a bench scraper instead of your hands to form it into a rectangle.  Wrap and then use a rolling pin to get it into a thinner slab.  Refrigerate at least an hour and can stay there for days.
To bake, roll out to the size of a 1/4 cake sheet pan size, crimp the edges.
Oven on to 350 degrees. 
Filling:
Cream butter and sugar.  Add eggs one at a time.  Add buttermilk, lemon juice, vanilla, and cardamom.  Beat until combined.
Add to pie crust, bake about 45 minutes on top of a pizza stone or baking steel.