Heat olive oil in a large pot over medium heat. Add the onion, carrots, and celery and cook until softened, about 4 minutes. Stir in the garlic and ginger and cook for 1 minute until fragrant.
Add the curry powder, cumin, garam masala, and turmeric to the pot. Stir and toast the spices for 30 seconds until aromatic.
Add the diced chicken, red lentils, diced apple, chicken broth, and coconut milk. Stir to combine and bring to a boil.
Reduce heat to low, cover, and simmer for 20 minutes until the lentils have broken down and the chicken is cooked through.
Stir in the lemon juice and season with salt and pepper to taste. Ladle into bowls and garnish with fresh cilantro.