The recipe for pumpkin reserves from Food.com has you place 8 cups of pumpkin pieces in a bowl, layer it with sugar, and let it sit in the refrigerator overnight before cooking it. The recipe for Portuguese Pumpkin Preserves requires you to begin cooking its ingredients on the stove right away.
After letting the pumpkin and sugar sit overnight, the recipe from Food.com has you drain the pumpkin juice in a saucepan and boil it for 10 minutes. After it boils, place the pumpkin into the saucepan along with the grated rind and chopped pulp of a lemon. Add a bag of cloves, in a cheesecloth bag so you don't have to pick them out, to the saucepan, cooking on a slow boil for 40 minutes until the pumpkin is clear. Once the preserves finish cooking, place them in sterile jars and seal them.
To make Portuguese Pumpkin Preserves, add 4 cups of peeled and diced pumpkin, 3/4 cup sugar, a large pinch of salt and a stick of cinnamon to a saucepan. Simmer this for about 20 minutes over medium heat until most of the liquid from the pumpkin evaporates. Remove the pot from the heat, and mash the contents with a potato masher. Add about a teaspoon of lemon juice, and return the mixture to the heat until it evaporates into a paste. Remove the cinnamon stick before serving.