Cut the 4 sides off each pepper and use the bottom piece (and trim off any white pith).
Place the peppers on a large baking sheet with the skin side down. Drizzle with olive oil and season with salt and pepper.
Roast for 25 minuteus until the edges just start to blacken.
Empty the peppers into a food processor with all the other ingredients except the olive oil, and whizz.
Pour the olive oil through the spout of the bowl adding bit by bit until you are happy with the consistency. Check seasoning, adjust and process again. It takes a few minutes before you get a lovely smooth texture.
Notes
Pesto freezes very well and can be done in small glass jars. This is a great way to preserve summers bounty for the wintery months.