Bring a large pot of water to a boil for the pasta. Once boiling, add salt and pasta, and cook to al dente.
While the pasta cooks, heat a large skillet over medium to medium-high heat with olive oil, 2 turns of pan. Add onions or leeks, garlic, asparagus and fennel, and sauté 3 minutes. Add peas or shelled fava to the vegetables and wilt in greens. Add lemon zest and juice then reduce heat to lowest setting.