Butter the inside of the mold along with with a piece of aluminum foil that’s big enough to cover the mold.
Sift (or gently whisk) together the flour, ground ginger, cinnamon, allspice, baking powder and salt.
Place the room temperature butter in the bowl of an electric mixer. Using the paddle attachment, beat the butter on medium high for 2-3 minutes until light and fluffy.
Add the granulated sugar and beat on medium for 2 minutes or so.
Mix in the eggs, one at a time on medium.
Add the freshly squeezed lemon juice and pumpkin puree and combine.
Add the dry ingredients and mix on low until combined.
Spoon the batter into the mold place the lid on the mold. Then put the covered mold into a pot that’s big enough to hold the mold with a few inches to spare around the mold. Fill the pot about halfway up the outside of the mold with hot water. Place the lid on the pot and bring the water to a simmer over medium low heat.
Check the water every so often to make sure it’s still just simmering. If it boils, the pudding might rise before it’s done and then sink. (That said, it’s not the end of the world if this happens!)
Steam the pudding for 1 ½ - 2 hours.
Carefully remove the mold from the pot of steaming water. I use potholders.
Cut the twine. Carefully remove the foil from the pudding mold. Insert a wooden skewer (or knife) near the center and if the crumbs look done, the pudding is done. If the pudding isn't done, replace the foil "lid" and gently put the mold back into the pot of water. Cover the pot with a lid and bring it back to a simmer and cook until done.
Let the pudding cool completely and then un-mold it onto a serving dish.
Serve with lightly sweetened whipped cream.
Notes
***If you don't have a pudding mold, you can make this in individual ramekins. Any size from 4-8 ounces will work. If you use 8 ounce ramekins, you'll have batter for about 10 puddings. Butter the inside of each ramekin. Fill ¾ of the way full with the batter. Place them in two 9 x 13 inch pans. Fill the pay ½ way up the sides of the ramekins. Cover tightly with a piece of buttered aluminum foil. I also tie kitchen twine around the foil to make sure it's on tightly.Bake in a preheated 350 F oven for about 40 minutes or until a toothpick inserted in the pudding comes out clean. Be careful when lifting the foil off the pan - there's steam in there. Use a metal spatula to carefully (don't burn yourself) remove the puddings from the water bath and allow to cool on a cooling rack.Top with whipped cream and serve them right from the ramekins!