Butter one side of each slice of bread. Place half the cheddar cheese on one non-buttered side of the bread.
Top with all of the Olives, onion, tomato slices and spinach. Season with salt and pepper to taste. Place the rest of the cheddar cheese on top.
Add the other slice of bread, butter side up.
In a non-stick medium skillet, heat 1 tbsp of butter at medium heat. Add the sandwich, and cook 3 to 5 minutes per side or until the bread is golden brown and the cheese is slightly melted.