In a large pot, heat sesame oil over medium heat until shimmering, about 1–2 minutes. Add diced onion and sauté until translucent and soft, about 5 minutes.

Incorporate minced garlic, grated ginger, ground cumin, ground coriander, and crushed red pepper flakes into the pot. Stir continuously for about 2 minutes until fragrant.

Add red lentils and sliced carrots to the pot. Toss gently for about 1–2 minutes to coat them with the sautéed spices.

Pour in vegetable broth and bring to a boil. Once boiling, reduce heat to low, cover, and simmer for 25–30 minutes until lentils and carrots are tender.

Allow soup to cool slightly for about 5 minutes. Blend until smooth using an immersion blender.

Return blended soup to low heat and stir in soy sauce and rice vinegar. Taste and season with salt and pepper as desired.

Ladle warm soup into bowls and garnish with toasted sesame seeds and fresh cilantro. Serve with lime wedges on the side.