Coat an 8-inch square baking pan with nonstick cooking spray

Add aquafaba and cream of tartar to a mixing bowl and mix with an electric mixer on high for 6 minutes until very fluffy. Add rum, vanilla extract, salt and 1/4 teaspoon nutmeg and whip for 3 more minutes until stiff peaks are formed.

Boil the water and agar agar for 3 minutes stirring frequently. Add sugar and boil for another 3 minutes stirring constantly over medium-low heat.

Turn off the heat and add the hot sugar mixture into the beaten aquafaba.  Add this mixture slowly while beating aquafaba with a mixer set to low for about 30 seconds.  This will turn the fluffy white mixture a little shiny. Pour mixture into the prepared pan and let set for about 1 hour.

Cut marshmallows into 1-inch squares (coat knife and spatula with nonstick spray if marshmallows are sticking. Combine cinnamon, powdered sugar and remaining nutmeg together in a bowl and toss marshmallows to coat with the mixture.