Add the chopped onion to a bowl with the lime juice, zest and sweet chilli sauce. Leave to let the acid in the lime juice, soften and take the edge off the onion.
Prepare the rest of the ingredients. Once the sweetcorn is cooked, drain and rinse under cold water until cooled then add to the onion mixture along with the remaining ingredients, mix well and serve with extra lime wedges.
Notes
This salsa will keep for up to 5 days in a sealed container in the fridge.