In Puglia, they roast the pepper whole in a very hot oven, usually a wood burning pizza oven, until the skins blister. This method softens and sweetens the peppers and makes them more easy to peel.
1. Preheat the oven to 400F(200C).
2. Wash and dry the peppers. Place peppers on a baking sheet, and roast in the preheated oven until beginning to blister. Turn over and continue to roast, about 30 min in all.
3. Cool the peppers in a bowl, covered with plastic wrap to keep in the moisture.
4. When cool enough to handle, peel the peppers and remove the seeds.
5. Mix the vinegar with the anchovy paste. If not using the paste add 2 pinces of salt to the vinegar.
6. Put the peeled peppers in a clean holder, mix with capers, garlic, vinegar mixture, and basil. Stir well to make sure that pepper can absorb flavor well.
7. cover and refrigerate for a day stirring occasionally.
For a sweeter alternative, substitute the vinegar with extra virgin olive oil in step 5 and 6.
Anchovy paste can also be replaced with 2 anchovy fillets.