In a large saucepot over medium-high heat, add the oil and then add the cayenne, cumin, coriander, turmeric, and garam masala. Stir the spices until toasted and fragrant, about 1 minute.
Stir in the onion, garlic, and ginger and cook until softened, 3 to 5 minutes.
Add the apple, tomato, bell pepper and lentils and stir to coat in oil and spices.
Add the coconut milk and stock and bring to a boil. Reduce the heat to a simmer, stirring occasionally, until the mixture is thick and mushy, 20 to 25 minutes.
Add in cooked turkey to heat through then season with salt, pepper, and lemon juice, if using. Serve with garnishes, if desired.