Lebanese-Style Red Lentil Soup

Bring chicken stock and lentils to a boil in a large saucepan over high heat, then reduce heat to medium-low, cover, and simmer for 20 minutes.
Meanwhile, heat olive oil in a skillet over medium heat. Stir in garlic and onion, and cook until the onion has softened and turned translucent, about 3 minutes.
Stir onions into the lentils and season with cumin and cayenne. Continue simmering until the lentils are tender, about 10 minutes.
Carefully puree the soup in a standing blender, or with a stick blender until smooth. Stir in cilantro and lemon juice before serving.