Preheat your oven to 350°F. Generously grease the bottom and sides of an 8-inch nonstick round cake pan with unsalted butter.
In a medium bowl, using a hand whisk, whisk together the eggs, coconut milk, stevia, and vanilla.
Whisk in the coconut flour. Keep whisking until the batter becomes smooth and free of lumps.
If the batter seems very thick, add 1-2 tablespoons of water, as I do in the video.
Using a rubber spatula, stir in the kosher salt and baking powder.
Using the same rubber spatula, transfer the batter to the prepared pan. Smooth the top out.
Bake until the edges are golden brown and pull away from the pan, and a toothpick inserted in the center comes out clean, about 20 minutes. The cake will not brown on the top.
Place the pan on a cooling rack. Let the cake cool for 15 minutes, then invert it, bottom side down, onto the cooling rack and allow it to cool for 15 more minutes before slicing it into 8 slices.
Video
Notes
Make sure your cake pan is truly nonstick. This is essential when baking with coconut flour. I purchase a new nonstick pan once a year. When working with canned coconut milk, it's very important to make it completely smooth before adding it to the batter. If it's not thoroughly combined, that would introduce too much liquid and not enough fat into the batter. It's not enough to shake thee milk in the can. You should stir it well once you've opened the can. The best way to do that is to pour the entire can contents into a bowl (use a spatula to get everything out of the can) and use a hand whisk. You can keep the leftovers in the fridge, wrapped in plastic wrap or in an airtight container, for up to 5 days. You can also freeze individual slices in freezer bags. Defrost them overnight or in the microwave at 50% power.