Spray the frying pan with low calorie cooking spray and cook the onions, chilli and chicken on a medium heat.
When the onion has softened and the chicken has browned slightly, remove from the pan and set aside.
Add the stock, onion powder and no added sugar lemon squash to the pan and bring to the boil.
Allow to simmer for a few minutes. Place half of the sauce into a jug and whisk in the xanthan gum a 1/4 of a tsp at a time. You will need to whisk well - and keep whisking!
When the right consistency is achieved, return the sauce to the pan and add the chicken.
Add the lemon slices and cook gently for another 5 minutes.
Stir in the pineapple and remove from the heat immediately.
Taste, and add a little granulated sweetener if it's a bit too sour.
Serve with your choice of accompaniment.