Bring a large pot of water to a boil. Salt well, then cook orzo, stirring occasionally, until tender but firm, about 7 or 8 minutes. Drain, rinse with cold water, and drain well again. Toss the orzo with the pesto. sun-dried tomatoes, roasted red peppers, olives, caramelized onions, and lemon zest. Taste and adjust salt and lemon, adding juice as needed. Serve over salad greens.