In a large bowl, combine the sugar, flour, corn starch, and cinnamon. Add eggs and
whisk until smooth. Gently stir in rhubarb. Line a 9-inch pie plate with
bottom pastry. Add the rhubarb filling then dot with butter. Roll out
remaining pastry to fit top of pie; place over filling. Trim, seal and
flute edges. Cut slits in top. Dot with more butter and sprinkle with
sugar.
Bake at 400° for 50 minutes or until crust is golden brown and
filling is bubbly. Cool on a wire rack. Store in the refrigerator.