01 - Bring a large pot of salted water to a boil. Add orzo and cook according to package directions until al dente. Drain pasta and set aside, reserving 1/4 cup of the cooking water.
02 - In a food processor, combine spinach, basil, Parmesan, pine nuts, garlic, lemon juice, salt, and pepper. Pulse until finely chopped. With the motor running, slowly drizzle in olive oil until a smooth, cohesive paste forms, scraping down sides as necessary.
03 - Transfer warm orzo to a large mixing bowl. Add spinach pesto and gently toss to combine, incorporating reserved pasta water as needed to achieve a creamy consistency.
04 - Taste and adjust seasoning with additional salt and black pepper if desired.
05 - Distribute orzo onto plates. Garnish generously with grated Parmesan and freshly ground black pepper. Serve immediately.