Place the paneer in a shallow non-reactive dish with all the ingredients except the oil and leave to marinate for at least 10 minutes.
Heat the oil in a pan. Once hot, add the pineapple and capsicum, cook for 2-3 mins then add the marinated paneer and cook well on all sides (about 3 minutes) over a medium heat. Make sure you stir it properly so that you don't burn the paneer.
Add the pineapple juice then bring to the boil and serve.