Roast the peppers. I prefer to roast them on a grill, over coals, but you can roast them in the oven as well, or over an open flame on top of the stove.
When the skin of the peppers becomes charred, put them in a bowl and cover with a plate, letting them "sweat" for 10 minutes.
Meanwhile mix the oil, vinegar, water, garlic, sugar and salt to create the dressing for the salad
Peel the burned skin off the peppers and put them in a new bowl. The skin should come off very easily. Make a few small cuts in the peppers, so that the inside infuses with the marinade as well.
Add the dressing over the peppers and put the bowl in the fridge for a few hours before serving them.