To cook the lentils cover with at least 3 inches of water. Bring the pot to a boil and reduce to heat to a simmer, check the lentils after 20 minutes for tenderness. Check every 10 minutes again. The time will depend on how old your lentils are. Drain and rinse lentils to slightly cool.
Combine lentils and vegetables in a large bowl.
In a small bowl whisk together the dressing ingredients, streaming the olive oil into the bowl to create an emulsion.
Stir into lentil mixture and refrigerate to allow flavors to blend, stirring occasionally.