Wrap the sweet potato in a wet paper towel and microwave for 5 minutes. Flip to the other side and microwave for another 5 minutes. If the sweet potato doesn't feel very soft at this point, turn it over again and microwave for an additional 3-5 minutes, or until it is very soft. As an alternative to microwaving, you can boil or roast the sweet potato in the oven.
Allow the sweet potato to cool completely. This step is important, because it will make the potato easier to peel and it will ensure the potato isn’t too hot to cause the eggs to cook in the cake batter.
Remove the sweet potato skin and discard. Mash the sweet potato until it is nice and creamy and measure out one cup of mashed sweet potato.
Preheat the oven to 350 degrees F and line a 9-inch square baking pan or round cake pan with parchment paper. You can also spray the pan with cooking spray if you don't have parchment paper on hand. Transfer the mashed sweet potato to a large bowl along with the almond butter, eggs, pure maple syrup, vanilla extract, and vinegar. Mix the wet ingredients until a thick sticky substance forms. Note: If your almond butter has been chilling in the refrigerator or has been kept in a cool place, microwave it for 20 to 30 seconds, or until it is soft and easy to mix.
Add the cocoa powder, baking soda, ground cinnamon, and sea salt (dry ingredients) to the bowl with the wet ingredients and mix well until a thick cake batter forms. If you’d like to add chocolate chips for added chocolate goodness, you can do so now (use up to 1 cup).
Transfer the cake batter to the prepared baking pan and spread it into an even layer.
Bake on the center rack of the preheated oven for 23 to 28 minutes, or until the cake tests clean. I test for doneness by inserting a digital thermometer into the center of the cake. The optimal temperature is between 190 and 205 degrees F.