Place the lentils and broth or water into a medium saucepan over high heat. Bring the liquid to a boil. Lower heat and simmer, uncovered, until the lentils are tender but not mushy, about 30 minutes.
Drain the lentils in a colander and return them to the saucepan. Cool completely, about 20 minutes.
Place the lentils, garlic, olive oil, tahini, lemon juice, cumin (if using), and salt into the bowl of a food processor fitted with an S-blade. Process until smooth, stopping to scrape down sides of bowl as needed.
Transfer the finished hummus to a bowl and drizzle with olive oil. Serve with pita wedges, crackers or veggies for dipping.