Pre-heat the oven to 200ºC.
In a small bowl mix the red wine vinegar with the sweetener and a pinch of salt. Mix in the sliced onions, cover and refrigerate until needed.
Spread the sweet potato chunks over a baking sheet, spray with the low calorie cooking spray and sprinkle over the smoked paprika. Season with a little salt and pepper and toss around to ensure the sweet potato is well coated. Place in the oven and cook for 15 minutes, until the sweet potato is just cooked. It should be soft, but still able to hold its shape.
Place the coconut milk in a frying pan, stir in the Cajun seasoning, garlic granules, lime juice and a pinch of salt.
Place over a medium to high heat and bring to the boil. Boil rapidly until the coconut milk has reduced by half and become the consistency of single cream. This should take 5-10 minutes depending on the size of your frying pan. If you are using a small frying pan it will need a little longer cooking.
Remove from the heat and stir in the black beans and coriander.
When the sweet potatoes are cooked, carefully stir into the bean and coconut mixture and return to the heat for a minute or 2 to ensure everything is well coated with the coconut sauce and heated through.
Warm the wraps in a microwave for a couple of minutes.
Fill the wraps with lettuce and sweet potato. Top with the diced tomatoes and the pink pickled onions, and a spoonful of fat free yoghurt if desired.
Serve 2 tacos per person, with some extra salad and your choice of accompaniment.