1. Preheat the oven to 200?C/400F/Gas Mark 6. Put the peppers on a baking tray and roast in the oven for 20-30 minutes, until deflated and slightly charred. Leave to cool then peel off the skins. Cut the peppers in half and discard the core and seeds. 2. Put the peppers and olive oil in a food processor and blend to form a pur?e. Add vinegar, salt and pepper to taste. 3. Using a potato peeler, shave the length of each asparagus stalk then, if necessary, cut off the end if it is woody. 4. Steam the asparagus for 6-8 minutes, until tender but firm. 5. Arrange the asparagus in an ovenproof dish and sprinkle with a little oil. Bake at 190?C/375F/Gas Mark 5 for 20 minutes. Pour sauce over asparagus and garnish with tarragon.