For the Crust
With machine running, add ice water in a slow, steady stream through feed tube. Pulse until dough holds together without being wet or sticky; be careful not to process more than 30 seconds. To test, squeeze a small amount together: If it is crumbly, add more ice water, 1 tablespoon at a time.
Divide dough into two equal balls. Flatten each ball into a disc and wrap in plastic. Transfer to the refrigerator and chill at least 1 hour. Dough may be stored, frozen, up to 1 month.
For the Pie Filling
4 cups chopped rhubarb
1 1/3 cups white sugar
6 tablespoons all-purpose flour
1/2 Cup Plain Latta Kefir
1 tablespoon butter
Preheat oven to 450 degrees F (230 degrees C).
Combine sugar and flour. Sprinkle 1/4 of it over pastry in pie plate.
Heap rhubarb over this mixture, and add in the Latta Kefir. Sprinkle with remaining sugar and flour. Dot with small pieces of butter. Cover with top crust.
Place pie on lowest rack in oven. Bake for 15 minutes. Reduce oven temperature to 350 degrees F (175 degrees C), and continue baking for 40 to 45 minutes. Serve warm or cold.