In a medium bowl combine red onion, vinegar, and salt. Press down on the onions to make sure all are covered by the vinegar. Cover; let stand at room temperature at least 30 minutes or chill in the refrigerator up to 3 days.
Meanwhile, cook rotini in boiling salted water until rotini is to desired doneness. Drain rotini; rinse with cold water to cool the pasta quickly. Drain well.
In a large bowl combine drained pasta, the sweet pepper, tomatoes, artichokes, salami and olives (but not the juice). Use a fork or slotted spoon to transfer the red onion slivers from the vinegar mixture to the pasta mixture; reserve vinegar in the bowl.
For vinaigrette, add olive juice, olive oil, garlic, and oregano to vinegar mixture in bowl. Whisk until well combined. Season to taste with freshly ground pepper. Pour vinaigrette over pasta salad. Stir until well combined. Serve right away or cover and chill up to 24 hours at this point.
Just before serving, stir in basil and, if desired, pine nuts. If desired, garnish the top with extra freshly ground pepper.