Prepare the Ingredients:

1. Prep Vegetables: Dice the onion, carrot, celery, and apple. Mince the garlic and ginger. Cut the chicken into bite-sized pieces.

Cook the Soup:

1. Sauté Aromatics: Heat the vegetable oil in a large pot over medium heat. Add the chopped onion and cook until translucent, about 5 minutes. Stir in the garlic and ginger, and cook for another minute.
2. Add Vegetables and Spices: Add the diced carrot, celery, and apple. Cook for 5 minutes, stirring occasionally. Add the curry powder, turmeric, cumin, coriander, paprika, and cinnamon. Stir well to coat the vegetables with the spices.
3. Brown Chicken: Add the chicken pieces to the pot and cook until they are no longer pink on the outside, about 5 minutes.
4. Simmer: Stir in the red lentils, coconut milk, and chicken broth. Bring to a boil, then reduce the heat and simmer for 25-30 minutes, until the chicken is cooked through and the lentils are tender.
5. Season: Season with salt and pepper to taste. Stir in the lemon or lime juice for a touch of acidity.

Serve:

1. Prepare Accompaniments: Cook basmati rice or warm naan bread if serving with the soup.
2. Garnish: Ladle the soup into bowls and garnish with fresh cilantro or parsley. Serve with a side of rice or naan bread.