Bring a large pot of water to a boil. Add pasta, and cook until al dente. Drain, reserving 1/2 cup cooking liquid.
Meanwhile, combine toasted pumpkin seeds, parsley, chives, oil, garlic, 1 teaspoon salt, the lemon zest, and 1 cup baby spinach in a food processor. Season with pepper, and pulse until well combined.
Toss pasta with pesto mixture. Add reserved cooking liquid, and mix until pasta is well coated. Fold in remaining 1 1/2 cups baby spinach. Sprinkle with remaining 1/2 teaspoon salt. Divide among 6 bowls. Top each with a dollop of ricotta, and season with pepper. Serve with tomato wedges if desired.