Prepare the black lentils. Add lentils and water to a stockpot over medium heat.
Simmer for 20-22 minutes, or until fork tender. Drain and set aside.
Prepare dressing. Add all dressing ingredients to a small bowl and whisk until smooth and creamy.
Assemble the salad by tossing together cooked and drained lentils, arugula, and dressing. Add avocado and mango and toss once more. Serve!