For a richer flavor, try roasting the squash with a drizzle of maple syrup or a sprinkle of brown sugar. If you don't have red onions, yellow onions will work as a substitute. Toasted pumpkin seeds can be used in place of pine nuts. For a vegan option, substitute the feta cheese with a plant-based alternative or nutritional yeast for a cheesy flavor. The salad can be served warm or at room temperature.