In a large pot, heat the vegetable oil over medium heat.
Add the chopped onion, carrots, and celery. Sauté until they become tender and fragrant, about 5 minutes.
Stir in the garlic and ginger and cook for another 2 minutes.
Step 2: Spice It Up
Add the curry powder, ground cumin, ground coriander, turmeric, and cayenne pepper to the pot. Stir well to coat the vegetables in the spices. Cook for 2-3 minutes to toast the spices.
Step 3: Simmer And Blend
Pour in the red lentils, diced tomatoes, and chicken or vegetable broth. Bring the mixture to a boil.
Reduce the heat to low, cover, and simmer for about 20-25 minutes, or until the lentils are soft and the vegetables are tender.
Step 4: Add The Finishing Touch
If using chicken breasts, remove them from the pot and shred them with two forks. Return the shredded chicken to the soup.
Stir in the coconut milk and lemon juice. Season with salt and pepper to taste.