Heat the olive oil in a large pot or Dutch oven over medium heat. Add the onions and sauté until they are translucent, about 5 minutes.
Stir in the carrots and celery, cooking for an additional 4-5 minutes until softened.
Add the minced garlic and grated ginger to the pot, stirring for about 1 minute until fragrant.
Sprinkle in the cumin, coriander, turmeric, and cayenne pepper. Stir well to coat the vegetables in the spices.
Add the diced chicken breast to the pot, cooking until no longer pink, about 5-7 minutes.
Stir in the rinsed red lentils, chicken broth, and chopped tomatoes. Bring the mixture to a boil.
Reduce the heat to low, cover, and simmer for about 30 minutes, or until the lentils are tender.
Pour in the coconut milk and stir in the spinach leaves. Cook for an additional 5 minutes until the spinach is wilted.
Season the stew with salt, pepper, and lime juice to taste.
Serve hot, garnished with fresh cilantro if desired.