Preheat oven to 350°F (175°C). Grease an 8-inch round cake pan and line the bottom with parchment paper.
In a large mixing bowl, whisk together the almond flour, cocoa powder, baking soda, and sea salt until thoroughly combined and free of lumps.
In a separate medium bowl, beat the eggs until slightly frothy. Whisk in the maple syrup, granulated sugar, melted butter, milk, and vanilla extract.
Gradually pour the wet ingredients into the dry ingredients. Use a whisk or silicone spatula to stir until the batter is smooth and no dry streaks remain.
Pour the batter into the prepared cake pan, smoothing the top with an offset spatula.
Bake for 30 to 35 minutes, or until a toothpick inserted into the center of the cake comes out clean or with a few moist crumbs.
Remove the pan from the oven and place on a wire rack to cool for 20 minutes.
Carefully run a thin knife around the edge of the cake and invert onto the wire rack to cool completely before slicing.