1. In a saucepan, combine lentils and water. Bring to a boil, then reduce heat and simmer for 20-25 minutes until lentils are tender. Drain and let cool.
2. In a large mixing bowl, combine cooked lentils, cherry tomatoes, cucumber, red onion, and parsley.
3. In a small bowl, whisk together olive oil, lemon juice, minced garlic, Dijon mustard, salt, and black pepper to make the vinaigrette.
4. Pour the vinaigrette over the lentil mixture and toss to combine. Serve chilled or at room temperature.