Adapted from Saveur
3 ¼ c. flour
14 Tbsp. unsalted butter, cubed and chilled, plus more, melted, for brushing
2 tsp. kosher salt
4 c. roughly chopped rhubarb
2 c.sugar, plus more for sprinkling
1 tsp. vanilla extract
Pulse 3 cups flour, butter, and 1 tsp. salt in a food processor until small pieces form. Add ½ cup ice water; pulse until dough forms. Remove dough from processor and roll into a ball; halve dough and press into two disks. Wrap with plastic and chill for 1 hour.
Heat oven to 350° F. Toss together remaining flour and salt, along with rhubarb, sugar, vanilla, and eggs, set aside. Unwrap dough and use a rolling pin to roll both disks into 11″-wide x 1⁄8″-thick circles. Transfer one circle to a 9″ deep-dish pie pan; mound filling inside. Place second dough circle over top of pie; trim and crimp edges. Brush pie top with butter and sprinkle with sugar. Bake until golden and bubbling (about 1 hr.). Let cool and serve with ice cream.