January 23rd is National Rhubarb Pie Day.
Rhubarb is an herbaceous perennial plant. They have short, thick edible rhizomes (stems) and large toxic leaves. The stalks are commonly used to make tarts and pies.Rubarb and strawberries is a popular combination.
Though rhubarb is technically a vegetable, in the United States, a New York court decided in 1947 that since it was used in the United States as a fruit, it was to be counted as a fruit for the purposes of regulations and duties. 
You can find rhubarb in the produce or frozen section of your supermarket.
Here is a recipe for Rhubarb Custard Pie
3 cups rhubarb, cut into 1/2 inch pieces
2 egg yolks
1 cup granulated sugar
2-1/2 tablespoons all-purpose flour
1 tablespoon butter
2 (9 inch) unbaked pie crusts, chilled
Place rack on the bottom of the oven.
Preheat oven to 425F.
Beat egg yolks until thick and frothy.
Gradually beat in the sugar, flour, and melted butter or margarine.
Stir in rhubarb pieces.
Pour rhubarb mixture into an unbaked pie shell.
Cover filling with top crust. Flute and vent the pie.
Bake 10 minutes, then reduce heat to 375F and bake 30 minutes.