All Jack-o-lanterns can be baked. But it's really only worthwhile to bake "pie" pumpkins. The larger pumpkins that are grown specifically for Hallowe'en have been crossbred to be large, watery, easy to clean and seed, and easy to carve. They taste bland and dull. "Pie" pumpkins are considerably more difficult to clean and carve but are best for eating. The smaller jackolantern in the photos is a pie pumpkin.
Here is the little pumpkin the next morning, just before being carved further for baking. (The larger pumpkin was broken up and is already languishing in the composter.)
Cut the pumpkin in half and remove any threads and seeds. If the stem is really large, remove it as well. Place the pumpkin pieces shell side up on a cookie sheet and bake at 325F until fork tender. This pumpkin was done after about 55 minutes.
Let the pumpkin cool then spoon the flesh into a sieve. Compost the skin.
Use the back of a spoon to push the pumpkin through the sieve. (Of course a food mill works perfectly for this too - but we don't have one.... You can also use a food processor but you risk leaving thready parts in the pumpkin.)
This little pumpkin produced just over two cups of pumpkin.
And why did I go to all this trouble? Just look at the picture of that cake in SAVEUR Magazine's November 2007 issue that is dedicated to American Thanksgiving. We nneeeeeeeed to try that cake! (Later: I made the cake! Please take a look at the photos.)