To make pumpkin puree, choose a 4- to 6-pound baking pumpkin, and have kosher salt available. This recipe takes about three hours and makes 2 to 2 1/2 pounds of puree.
Heat an oven to 400 degrees F, and wash and dry the pumpkin. Slice off a small piece of pumpkin skin from one side so that the pumpkin does not roll when on its side. Remove the stem, and use a cleaver and mallet to cut the pumpkin in half from the bottom to top. Scoop out all of the fiber and seeds, saving the seeds for roasting if desired.
Sprinkle the pumpkin's flesh with salt, and lay each half with the flesh down on a sheet pan, making sure to place parchment paper on the surface before the pumpkin. Roast the pumpkin for about 30 to 45 minutes or until a paring knife can easily insert into the pumpkin, testing in several areas to ensure it is completely done.
Remove the sheet pan, and place the pumpkin halves on a cooling rack for about one hour. With a large spoon, remove the flesh of the pumpkin from the skin, and place it into a food processor. Process the flesh until it is smooth, usually about three to four minutes. Store the puree in the refrigerator for up to one week, or freeze it for up to three months.