Halve the squash lengthwise and remove the seeds and strings. Rub the insides with 2 tablespoons softened butter; season with salt and pepper. Place on a roasting pan, skin side down. Bake in a preheated 350 degree oven for 30 to 40 minutes or until fork tender. Remove the squash from the oven, scoop out the flesh and place in a food processor. Blend until smooth.