In a large skillet over medium heat, melt 1 tablespoon butter. Add onion and sauté until tender; about 10-12 minutes. Add 1 tablespoon curry powder; cook for an additional minute, stirring constantly. Add apples, juice and currants; continue to cook until liquid evaporates. Season to taste with salt and pepper; remove from heat.
Preheat oven to 350° F. In a small skillet over medium heat, melt remaining 5 tablespoons butter. Add remaining ½ tablespoon curry powder and cook for 1 minute; remove from heat.
Lightly brush a rimmed baking sheet with some of the curry butter. Arrange squash discs in a single layer on buttered baking sheet. Sprinkle discs with salt and pepper. Divide apple filling evenly on tops of discs. Drizzle remaining curry butter over discs. Cover loosely with foil and bake until squash is tender; about 40-45 minutes.
Using a spatula, transfer discs to serving platter.