You will need
Adjust oven rack to middle position. Preheat oven to 200°C.
Cut each onion into eight wedges. Halve the peppers lengthways and cut each half into 4 long strips.
Roast open for ± 30 minutes until nicely browned. Spoon out the vegetables and add another ½ cup of Vinaigrette to the pan juices, stir over heat until everything is amalgamated. Decant this dressing into a screw top bottle and keep in the fridge.
Line a platter with leaves, dot with roasted vegetables. Drizzle with reserved dressing and finally grind over some freshly ground black pepper.