Lightly grease a 9X9 inch baking pan and set aside until needed
Add the egg whites and cream of tartar to a medium mixing bowl and use a hand blender to whip until stiff peaks form - Set aside until needed
In another medium mixing bowl, beat the egg yolks and confectioners’ sugar together until fully incorporated and pale yellow
Add the butter, vanilla extract, and Pumpkin Spice to the yolk/sugar and blend until well combined
Add the flour in 3 batches and mix until well combined
Add the pumpkin purée, salt, and ½ Cup of the half and half - Mix (scraping down the sides as needed) until well combined
Gradually mix in the remaining half and half until well combined
Using a spatula, gently fold in the egg whites (From Step 3) until well incorporated
Pour into prepared baking pan and place on the center rack of the oven
Allow to bake for 60-65 minutes until set but still slightly ‘jiggly’ in the center
Remove from oven and allow to cool completely to room temperature - Cover, and place in the refrigerator for a minimum 1 hour (up to 12 hours) before cutting into squares
Serve chilled, warm, or at room temperature topped with a dusting of confectioners’ sugar, topped with whipped cream, à la mode, drizzled with maple syrup or caramel, topped with pecans, or any combination you can imagine