Heat the oil in a large non-stick frying pan over medium heat. Add the onion and cook, stirring, for 2 mins or until onion softens. Season the chicken. Add to the pan and cook for 2-3 mins or until just brown all over.
Add the simmer sauce, tomato, lentils and stock to the chicken mixture and stir to combine. Bring to a simmer. Cover partially and cook, stirring often, for 20 mins or until lentils are tender, chicken is cooked through and sauce thickens. Season.
Top the curry with the yoghurt. Season to serve.
Serve with naan bread, lime wedges and coriander sprigs