Place a large pot of water over high heat to boil the pasta. When the water reaches a bubble, salt it, drop the pasta in and cook to al dente according to package directions. Just before draining the pasta, reserve a mug of starchy cooking water then drain and reserve.
While the pasta is cooking, place a large skillet over medium-high heat with 2 turns of the pan of EVOO, about 2 tablespoons. Add the onion and garlic to the pan, and cook until just tender, about 4 minutes. Add the asparagus and green beans to the pan and continue cooking for another 1 minute.