Preheat your oven to 350°F (177°C). Grease an 8 x 11–inch (20.3 x 28–cm) baking dish and line with parchment, letting the excess fall over the sides.

In a large bowl, mix together the butter, pumpkin puree, brown sugar, granulated sugar, water, eggs and vanilla until well blended.

In a small bowl, whisk together the flour, cinnamon, baking powder, baking soda, salt, allspice, nutmeg, ginger and cloves. Pour the flour mixture into the butter mixture and stir until just combined. Spoon the batter into the prepared baking pan and smooth the top with the back of the spoon.

Bake for 40 minutes on the center rack. Let cool completely in the pan.

Add the egg whites, sugar, corn syrup, cream of tartar, and salt to the clean bowl of an electric stand mixer and nestle it in a saucepan of simmering water over medium-high heat. Do not allow the bottom of the bowl to touch the water. Whisk until the mixture is opaque, frothy, the sugar is melted (rub some between two fingers, if it feels gritty, keep whisking) and warm to the touch. Remove the bowl from the heat and transfer it to the stand mixer fitted with the whisk attachment. Mix on medium-high speed until stiff and glossy and cool to the touch, about 3-5 minutes. Add the vanilla and run the machine for 30 seconds more.