In a bowl mix all the ingredients for the dough except for the butter. Knead the dough on floured surface, until the dough is no longer sticky. Roll the dough in a long sausage, 2 inches in diameter. Cut it into small portions. Bring the water to a boil, add salt. Put your dumplings in a boiling water. Carefully draw a spoon on the bottom of the pan to be sure that dumplings is not stuck. When the dumplings float, cook them for another 2 minutes. Drain and add a bit of butter. For the sauce, pour the blueberries in a small saucepan, add sugar and lemon juice. Cook over medium heat stirring occasionally, until berries will not let the juice. Serve dumplings immediately, with a blueberry sauce on top.