Steep tea in 1 cup of boiling hot water and allow it to sit until cool. If using loose leaf tea, strain before dipping your lady fingers.
Once the tea is cool, make the pumpkin mascarpone. In a stand mixer fitted with the paddle attachment, or with a handheld mixer, beat the mascarpone, sugar, egg yolks, rum, heavy cream, pumpkin puree, and vanilla on medium high speed until light and fluffy, about 2-3 minutes.
Get your lady fingers, tea, and loaf pan ready for assembly. Dip one lady finger into the tea and rotate quickly to saturate, then gently lay in the loaf pan. Repeat the process until the bottom of the pan is covered.
Cover the first layer of lady fingers with half of the pumpkin mascarpone mixture, then repeat the dipping and layering process of the lady fingers. Add the remaining pumpkin mascarpone and smooth into a very clean and flat layer.
Cover the tiramisu with cling wrap and allow it to sit in the fridge for at least 6 hours, but preferably overnight.
Before serving, remove the cling wrap and combine the cocoa powder and cinnamon. Sift the mixture over the top to cover completely, then wipe down the edges of the pan with a damp paper towel to create clean edges.
Slice or scoop and place onto plates or bowls.