Cook the pasta in a large pot of salted boiling water according to package directions.
While pasta is cooking, add sunflower seeds, oil, crushed tomatoes, tomato paste, salt, black pepper, lemon juice, and basil in a high-speed blender or a food processor.
Blend until smooth.
Taste and add more salt or basil if needed, and blend again.
Toss the cooked pasta with the pesto in a large bowl.
Top with sunflower seeds for some crunchiness and garnish with basil leaves.