Preheat the oven to 350 degrees. Grease a 9x13 cake pan and set aside.

Add the egg whites and 1/2 cup sugar to the bowl of a stand-up mixer (with the whisk attachment) and beat on high until stiff peaks about 3 to 4 minutes. Scoop it out and put it into another bowl.

Place the bowl back on the stand-up mixer (no need to clean it out) and add the remaining 1/2 cup sugar and egg yolks. Beat until pale yellow and double in volume. Next, mix in the pumpkin puree and vanilla.

Place a sieve atop the bowl on the stand-up mixer and sift in the flour, baking powder, pumpkin spice and salt. Mix until just combined.

Fold in the egg whites until you no longer see any speckles of remaining egg white.

Pour the batter into the prepared 9x13 cake pan and transfer to the oven to bake for 15 to 18 minutes, until a skewer when inserted into the center comes out clean. Let cool completely in the pan before proceeding with the rest of the recipe.

In a large measuring cup, add the coconut milk, whole milk and condensed milk. Whisk until combined. Using a skewer or fork, create little holes on the top of the cake. Pour the milk mixture over the cake (it may seem like a lot but it will absorb!). Transfer to the fridge to 2 to 3 hours, ideally overnight.

Just before serving, top the cake with fluffy whipped cream and dust with cinnamon or pumpkin pie spice. Slice and serve.