Combine the lentils, lemon juice, and olive oil. Set aside.
Finely chop the herbs. Combine the herbs, cucumber, tomato, and onion in a mixing bowl. Stir in the lentils.
Season to taste with the sumac, salt and pepper right before serving.
In a medium saucepan, combine the lentils, bay leaf, and water and bring to a boil. Cover, reduce the heat, and simmer, stirring occasionally, for 15 to 18 minutes or until tender but not mushy. Drain and let cool.
