In a large pot, heat sesame oil over medium heat. Add diced onion and sauté for about 5 minutes until translucent.

Stir in minced garlic, grated ginger, ground cumin, ground coriander, and crushed red pepper flakes. Cook for another 2 minutes.

Add rinsed red lentils and sliced carrots; mix well to coat them in the aromatic mixture.

Pour in vegetable broth and bring to a boil. Reduce heat, cover, and simmer for 25–30 minutes until tender.

Remove from heat and cool for 5 minutes. Blend the soup until silky smooth with an immersion blender.

Stir in soy sauce and rice vinegar. Season with salt and pepper. Reheat gently if necessary.

Ladle soup into bowls and garnish with toasted sesame seeds, cilantro, and lime wedges.