2) Place the onion in a small bowl of cold water. Place the tomatoes in a large bowl and season with 1 tsp of salt and some pepper. Chop the oregano with the garlic and the remaining 0.5 tsp salt. Use the flat side of the knife to mash and smear the mixture to a coarse paste. Scatter the garlic mixture over the tomatoes.
3) Cut the pepper about the same size as the tomatoes and add to the salad. Drain the onions, pat dry, and add to the tomato mixture. Add the vinegar and olive oil and toss together. Add the drained pasta and toss well. (The salad can be prepared 2 hours in advance and refrigerated.)
4) Before serving, mix the rocket leaves into the salad, then add the cheese and toss lightly. Taste the salad and season with salt and pepper, to taste. Serve.
Cook's Note: A single pepper can be roasted directly on a gas burner. Lay the pepper directly over a high flame and cook, turning as needed, until the skin blisters and blackens. When the pepper is completely charred transfer it to a medium bowl, cover with a plate or lid and allow to cool completely. To peel the pepper, wrap it in a paper towel and rub off the charred skin.
With an electric hob or for more than 1 pepper, preheat the oven grill. Cut the peppers in half through the stem. Remove the seeds. Lay the peppers cut-side down on a roasting tin. Set the pan on the uppermost rack closest to the grill. Cook until the skin chars, about 5 to 10 minutes. Rotate the pan, as necessary, so the peppers char evenly. Cool covered, then peel.