1 1/2 cups heavy cream, whipped (or whipped coconut cream for Paleo), optional
1 pint berries (optional)
Preheat the oven to 350ºF and adjust the rack to the middle position.
Place the egg whites and lemon juice in the bowl of a standing mixer. Whisk the egg mixture on medium-high until foamy, about 30 seconds. Add the salt, cream of tartar and vanilla. Whisk the mixture on medium-high until soft peaks form, about 1-2 minutes.
With the mixer on medium-high, slowly add 1/2 cup of the maple sugar, 1 tablespoon at a time. Sift the remaining 1/4 cup maple sugar and arrowroot flour into a small bowl. With the mixer on medium, slowly add the arrowroot mixture. Turn the speed up to medium-high and whip until smooth (there might be some tiny little lumps from the sugar, but it will melt in the oven while baking).
Pour the batter into a clean (and NOT oiled), 12-cup angel food cake pan (I'm still on the look-out for a glass or stainless steel angel food cake pan. If you know where to purchase one, please let me know!). Bake for 40-45 minutes, until cake is puffed and the top is just turning golden brown.
Remove the cake from the oven. Carefully turn the cake upside-down and place on top of a can. Let cool completely, about 1 hour. Run a knife around the outside of the cake and invert onto a cake platter (you might need to shake the cake a little to get it to separate from the center tube of the cake pan). Serve alone or with whipped cream and berries.
Note: I only test the recipes on my site with the listed ingredients and measurements. If you would like to try a substitution, you are welcome to share what you used and how it turned out in the comments below. Thanks!