In a large saucepan on medium heat, heat oil and saute onion for 4-5 minutes without browning. Add garlic and ginger and cook for 1 minute.
Add the curry powder, cumin and pepper and stir to coat onions. Add the prepared Whole Green Lentils, coconut milk and stock. Stir and cover. Simmer for 15 minutes, adding more stock or water if the mixture looks dry.
After 15 minutes, add the prepared Red Split Lentils and cook for a further 10 minutes, stirring and adding more liquid if necessary.
Fold in the spinach, lemon juice and chopped coriander. Heat through and serve with rice and naan bread.