Preheat oven to 425 degrees. Generously butter a rimmed baking sheet.
Halve 2 medium acorn squash crosswise. Scoop out seeds; discard. Slice a small piece off bottom of each squash half, just enough to level. Set squash halves, scooped sides down, on prepared sheet. Bake for 20 to 25 minutes.
Turn squash over; prick insides all over with a fork. Divide 2 tablespoons butter and 2 tablespoons light-brown sugar among halves; season with coarse salt and ground pepper. Continue to bake until flesh is easily pierced with the tip of a paring knife, 20 to 30 minutes more. Serve warm drizzled with pure maple syrup.