Slow Cooker Method: Preheat small skillet on low-medium heat and swirl oil to coat. Add onion and garlic, cook until golden brown (5 minutes), stirring occasionally.
Add turmeric, coriander, curry powder, cumin and salt; cook for another 30 seconds, stirring frequently. This will allow the depth of flavour in spices to develop. Transfer to a slow cooker and add coconut milk, tomato paste, water and lentils. Stir to combine, cover and cook on High for at least 3 – 4 hours or on Low for 6 – 8 hours.
Serve hot garnished with cilantro/green onions.