Place the prunes in a large saucepan, and add water to barely cover while you peel and cut the potatoes and carrots. Add the potatoes, carrots, lemon juice, and sugar to the water, bring to a boil, and lower heat. Simmer the mixture until the carrots are very tender and the mixture is thick, about 1 hour, stirring every 20 minutes.
If a thicker tzimus is desired, stir in the matzo meal and simmer an additional 30 minutes.
