To make the dressing, finely chop the garlic and place in a bowl. Add the brown sugar, vinegar, lime juice, salt and pepper then whisk until the sugar has dissolved.
Whilst still whisking, drizzle in the olive oil.
Finely chop the red onion and add to a large bowl along with the chilli flakes.
Finely chop the tomato, red pepper and avocado (or leave larger if you prefer a chunkier salsa) and add to the bowl.
Roughly chop the coriander and parsley and add to the bowl.