Shallot vinaigrette: In small bowl, whisk together olive oil, lemon juice, mustard, shallot, salt and pepper. Set aside.
Salad: In saucepan, bring lentils and 3 cups water to boil. Reduce heat, cover and simmer until lentils are tender, 15 to 20 minutes; drain. Let cool slightly.
While lentils are cooking, in large bowl, toss together sweet potato, olive oil, garlic powder, paprika, pepper and salt. Arrange in single layer on greased rimmed baking sheet. Roast in 425°F oven, turning once, until tender, 15 to 18 minutes. Scrape onto plate; wipe pan clean.
Arrange halloumi in single layer on pan; broil until golden, about 3 minutes. Remove to cutting board; chop.
In separate large bowl, combine lentils, sweet potato, halloumi and cilantro. Drizzle with Shallot Vinaigrette; toss to coat.