Caramelized Onion and Lentil Soup

In a medium saucepan, heat oil over medium-high. Add onion and cook, stirring occasionally, until soft and edges are browned, about 15 minutes. Add lentils and broth and season with salt and pepper. Bring to a boil; reduce to a medium simmer and cook, gradually smashing some lentils against the side of pan with a spoon to thicken soup, 10 minutes. Serve topped with a dollop of yogurt and herbs.