This time of year, when the Rhubarb is coming up, is when I pull out this recipe I got from my mother-in-law. Its also great with other fillings. We have tried apples, blackberries, and raspberries too.
For sauce: In a sauce pan, combine sugar, flour, cinnamon and salt. Stir in water. Add butter. Bring to a boil; cook and stir 1 minute. Remove from heat. Add vanilla; set aside.
For dough: In a medium bowl combine flour, sugar, baking powder and salt. Cut in butter until mixture resembles coarse crumbs. Add milk and mix quickly. Do not over mix. Gather dough into a ball and roll out on a floured surface into a 9"x12" rectangle.
Spread dough with softened butter; arrange rhubarb on top. Combine sugar and cinnamon; sprinkle over rhubarb. Roll up from the long side and place on a cutting board seam side down. Cut roll into 12 slices. Arrange slices in a greased 9"x13" baking dish. Pour sauce over. (It will be liquidy, thats okay)Bake at 350 degrees for 35-40 minutes or until golden brown.