Heat oven to 375º.
In a medium-size sauté pan over medium-high heat, melt butter and cook onion until softened, about 5 minutes.
Add ham and spinach. Cook until most liquid has evaporated. Transfer to a large bowl.
In a separate bowl, beat eggs with half-and-half, seasonings, and cheese. Add to spinach mixture, blend, and pour into pie shell.
Bake 40 minutes or until set. Cool and serve.