Preheat your oven to 375 degrees F and line an 8-inch or 9-inch springform pan with parchment paper. Grease or oil the sides of the pan as well to help release the cake after baking.
Chop the chocolate and place it in a saucepan along with the coconut oil and coconut milk. Heat over low heat, stirring constantly until the chocolate is melted, making sure not to bring the mixture to a boil. It should be warm enough to melt the chocolate without becoming too hot.
Add the cocoa powder, sweetener, vanilla extract, and sea salt to the saucepan, stirring until everything is well combined.
In a separate bowl, whisk the eggs until fully beaten. Gradually pour in the chocolate mixture and stir until smooth and fully incorporated.
Pour the batter into the prepared springform pan and set it on the center rack of the preheated oven. Bake for 30 to 35 minutes, or until the center of the cake is set. (For best results, bake for 30 minutes, then turn off the oven and leave the cake inside for an additional 5 minutes while the oven cools.)
Allow the cake to cool for at least 45 minutes before removing it from the springform pan. Slice and serve.