This recipe comes from Everyday Food. They say that "Long cooking in a covered pot concentrates the sweet, nutty flavor of squash. If the vegetable begins to brown as it cooks, lover the heat and add a splash of water."
2 tablespoons olive oil
1 medium onion, thinly sliced
4 yellow squash (8 ounces each), thinly sliced
coarse salt and ground pepper
In a large pan, heat the oil over medium-low. Add onion, squash, and 2 tablespoons water. Season with salt and pepper and toss well. Cover and cook, stirring occasionally until soft, 30 to 35 minutes. Serves 4.