Bring a large pot of water to a boil. Salt the water, add the pasta and cook until al dente.
Toast the pine nuts in a small skillet over low heat, shaking the pan occasionally, until golden, about 3 minutes; let cool.
In a food processor, pulse to chop the toasted pine nuts, parsley, basil, tarragon, cheese, garlic and lemon juice. Turn on the processor and stream in 1/3 cup of the EVOO. Process until a thick pesto forms; add the remaining EVOO if needed. Season to taste with salt and pepper and pulse again to incorporate.
Place the pesto in a large, shallow serving dish. Add the peas and red bell pepper. When the pasta is almost cooked, add a ladle of its starchy cooking water to the pesto and mix. Drain the pasta well. Stir the celery and scallions into the sauce, add the pasta and toss to coat. Adjust the seasonings to taste.