Preheat the oven to 400 F. Put the onion, garlic, and peppers in a roasting pan. Drizzle the oil over the vegetables and mix, turn the pieces of pepper skin-side up. Roast for 25-30 minutes, until slightly charred, allow to cool slightly.
Squeeze the garlic flesh out of the skins into a food processor/blender. Add the roasted vegetables, orange rind and juice, tomatoes, and water. Process until smooth.
Press the mixture through a strainer into a bowl using a champignon (if you don't have a champignon, use the bottom of a large ladle or the back of a wooden spoon). Season well and chill for 30 minutes.
Make the Parmesan toasts when you are ready to serve the soup.
Preheat the broiler to high. Tear the baguette in half lengthwise, then tear or cut it across to make four large pieces. Spread the pieces of bread with butter.
Pare most of the Parmesan into thin slices or shavings using a swivel-bladed vegetable knife or a small paring knife, then finely grate the remainder.
Arrange the sliced Parmesan on the toasts, then dredge with the grated cheese. Transfer the cheese-topped baguette pieces to a large baking sheet or broiler rack and toast under the broiler until topping is well browned.
Ladle the chilled soup into large shallow bowls and sprinkle with chopped fresh chives (optional) and plenty of freshly ground black pepper.
Serve the hot Parmesan toast with the chilled soup.