Steam half of spinach, covered, for 5 minutes or until the spinach wilts; place steamed spinach in a colander. Repeat procedure with remaining spinach. Cool slightly, and squeeze dry.
Place spinach in a bowl. Add onions and remaining ingredients; toss mixture well to combine. Serve chilled or at room temperature.
You will need to steam the raw spinach in two batches, since there is so much of it. Combining the cool ingredients with your hands is easiest.