Place the oil and sliced onion in a wide, deep pan and fry gently with the lid on for 3-5 minutes until the onion is softened, but not brown. Stir occasionally.
Add the garlic, ginger, chilli, garam masala and turmeric and fry for 1 more minute over a gentle heat, with the lid off. Stir occasionally and, if the pan starts to get a little dry, add a small splash of water.
Add the red lentils and coconut milk, followed by the diced chicken and peppers, plus salt and pepper to taste.
Bring to the boil, then simmer for 20 minutes, or until the lentils are soft and the chicken is cooked through. (See Note 1) Stir occasionally and add a splash of water if the curry starts sticking to the pan, before it is fully cooked.
Finally stir through the lime juice and fresh coriander, and serve with your choice of rice / cauliflower rice / naans and all your favourite sides.