To assemble the galettes, roll out the dough to a 14" circle or two 7" circles. Place the crust(or two smaller ones) on a baking sheet. Mix together the 1/4 C flour along with 2 tbsp sugar and 1 tsp cinnamon and pour evenly over the crust leaving 1" for small galettes and 2" for the large galette around the outside edge. Top with rhubarb, mounding in the middle. Sprinkle the remaining sugar evenly over top. Using 1/3 C minus the 2 tbsp sugar mixed in with the flour will yield a fairly sour filling, so add a little more if you'd prefer a sweeter filling. To form, fold up the edges of the crust over the sides of the filling making sure to press the folds together slightly or they will come apart while baking. Brush the crust with melted butter and sprinkle with coarse sugar.