Preheat the oven to 200F and set a baking rack over a large sheet pan. Preheat a classic (not Belgian) waffle iron.
In a large bowl, beat the egg whites with the salt and cream of tartar until they hold stiff peaks.
In another large bowl, whisk together the almond flour, sweetener, and baking powder. Stir in the almond milk, egg yolk, butter, and vanilla extract. Carefully fold in the beaten egg whites until no streaks remain.
Lightly grease the waffle iron, then add about 1/4 to 1/3 cup batter to the center of the waffle iron. Cook until the waffles are golden brown on both sides. You should get at least 4 (four) 8-inch waffles.
Place cooked waffles on the prepared baking rack and place in the oven for 20 minutes, to crisp up. Break the waffles into sections.
Cinnamon "Sugar" Coating
In a shallow bowl, mix together the sweetener and the cinnamon. Brush each waffle section lightly with the melted butter, and then dip each in the cinnamon mixture.
Chocolate Sauce
In a small saucepan, heat the cream over medium heat until bubbling. Add the chopped chocolate and let sit to melt for 5 minutes. Whisk in the sweetener and vanilla extract until well combined. Let sit a few minutes to thicken.
The sauce will continue to thicken as it cools. To thin it out, whisk in a bit of almond milk.