Preheat the oven to 350 degrees F (175 degrees C).

Place squash, cut-sides down, in a 9x13-inch baking dish. Pour 2 cups water into dish around squash.

Bake in the preheated oven until tender and easily pierced with a fork, about 1 1/2 hours, adding more water as needed if pan looks dry.

Remove from the oven; transfer each half to a plate, cut-side up.

Top each half with butter and season with salt and pepper.