Heat a large non-stick skillet over medium heat. Butter bread slices. Add 4 slices bread, buttered side down, to skillet. Top each with 1/4 cup chili, 1/2 cup cheese and 2 tablespoons onions. Top with remaining bread, buttered side up. Cook over low heat for 3-4 minutes per side until bread is nicely browned and cheese is melted.