1. Oil an 8-cup lidded pudding mold with vegetable oil; set aside.

2. Peel persimmons and transfer to a medium bowl. Mash flesh, removing black seeds (you should have 2 3/4 cups of pulp); set aside. In the bowl of an electric mixer fitted with the whisk attachment, whisk together sugar and eggs on medium-high until fluffy, about 5 minutes. Add oil and vanilla; mix until well combined. Add persimmon pulp and mix to combine.

3. In a medium bowl, whisk together flour, baking soda, salt, and cinnamon. Add to persimmon mixture and mix just until smooth, scraping down sides of bowl once during mixing. Transfer mixture to prepared mold and cover with an oiled parchment paper round; cover mold with lid.

4. Bring a kettle of water to a boil over high heat. Fit a large pot with a rack and place filled pudding mold on rack in pot. Add just enough boiling water to come halfway up the mold. Place pot over high heat and bring to a boil; immediately reduce heat to a simmer and cook until pudding springs back when touched, about 2 1/2 hours, adding more boiling water as necessary to maintain water level.

5. Remove mold from pot and uncover. Let pudding cool in mold for 1 hour, then carefully run a sharp knife around the top edge of the pudding to loosen from the mold and invert carefully onto serving platter. Serve with sour lemon sauce.