In a large sauté pan, heat the olive oil over medium heat and sauté the onions until golden, 6 to 8 minutes. Add the orange zest and garlic and cook until softened, 2 to 3 minutes. Reduce the heat to low and add the chicken stock. Simmer, uncovered, for 10 minutes, or until slightly reduced. Meanwhile, in a large pot of salted boiling water, cook the pasta until al dente, then drain. Toss with onion mixture; add the capers, parsley, salt and pepper. Delicious as a main course, or served as a side dish with grilled seafood or chicken. Serves 4