I substituted sucanat for the brown sugar and spiced with cinnamon, ginger and nutmeg. Instead of mixing the butter, I just added a pat on top of the sucanat and spice mixture. It's very simple and tasted fantastic. We drizzled a little maple syrup on top.
I've found cooking acorn squash is very easy in a microwave. Place cut side down on a plate and cook on high until soft. Time depends on power and size of squash - about 6-8 minutes for one half. Turn right side up and prick flesh or stir up in shell. Add salt, pepper, butter, brown sugar and reheat to melt, or lite maple syrup to save calories.