To make the curry paste, spray the pan with low-calorie cooking spray. Add the onion and garlic and cook over a medium heat for 5 minutes until softened.Put the cooked onion and garlic in a blender with the rest of the curry paste ingredients and a pinch each of salt and pepper and blend into a paste. Put the chicken in a bag or bowl with the paste, making sure to coat it well. Marinate the chicken for at least an hour in the fridge.
After marination add the chicken to a medium frying pan with the peppers and some low-calorie cooking spray. Sauté over a medium heat for 5 minutes, until the peppers have softened and the chicken has browned.
Add the tomatoes and stock and simmer over a medium heat for 15 minutes until chicken cooked through and sauce thickened.