Dice the tomatoes and cut the leek into julienne strips; set aside.
In a blender or food processor, combine the basil, pistachios, salt, grated Parmesan, olive oil, and garlic. Blend until mostly smooth. Set aside.
Bring a large pot of salted water to a boil.
In a medium saucepan, heat 1 tablespoon olive oil over medium heat. Add the leek and cook until soft. Add the tomatoes, salt, and pepper. Cook 7–10 minutes until soft.
Boil pasta until al dente.
Stir the pesto into the tomato mixture. Drain the pasta and mix it in.