Reserve some scallion greens, basil, and tarragon for serving.
Bring a large pot of water to a boil. Generously salt the water, then add the pasta. Cook for 2 minutes less than the package's directions, about 6 minutes.
Meanwhile, melt 2 tablespoons of butter in a large, deep skillet over medium heat. Add the scallions and a pinch of salt. Cook, stirring, until bright green and wilted, about 2 minutes.
Add the peas and 1/2 cup pasta cooking water. Cook, stirring, until heated through, about 2 minutes.
Using tongs, transfer the pasta to the skillet, along with the basil, tarragon, and remaining tablespoon of butter. Gently toss until the herbs wilt and the pasta is al dente and coated, 1 to 2 minutes. If the mixture seems dry, add more pasta cooking water 2 tablespoons at a time. Season to taste with salt and pepper.
Divide the pasta among serving dishes and zest the lemon directly on top. Cut the lemon into wedges and squirt lemon juice over each dish. Garnish with the reserved scallion greens, basil, and tarragon and serve.
Recipe by Genevieve Ko.