Put yeast, lukewarm water and 3 tablespoon flour in mixing bowl and let stand for 30 minutes. In large bowl put onion puree, potato puree, salt, and water. Add yeast, 7 cups flour, and caraway seeds. Beat well, mixing and adding flour until dough is no longer sticky. Turn out on floured board and knead until dough is smooth and elastic. Put dough into greased bowl and cover. Let rise in warm place until doubled in bulk. Punch down and shape into 3 round loaves. Put loaves into greased 10 inch round pans to rise. Cover and let rise almost doubled. Preheat oven to 400°. Brush tops of bread with water and bake for 1 hour until crusty. Cool on racks.