In a large pot, heat the sesame oil over medium heat. Add the chopped onion, diced carrots, and cook for about 5-7 minutes until the onions become translucent.
Stir in the minced garlic and grated ginger, cooking for an additional minute until fragrant.
Add the rinsed lentils, vegetable broth, soy sauce, chili paste, and ground cumin to the pot. Stir well to combine.
Bring the mixture to a boil, then reduce the heat to low and simmer for about 25-30 minutes, or until the lentils are tender and the soup has thickened.
Season with salt and pepper to taste. If you prefer a smoother texture, use an immersion blender to puree part of the soup, leaving some chunks for texture.
Toast the sesame seeds in a dry skillet over medium heat until golden brown; this should take about 2-3 minutes. Keep an eye on them, as they can burn quickly.
Serve the soup hot, garnished with toasted sesame seeds, fresh cilantro, and a lime wedge on the side for squeezing.