Heat oven to 350 degrees. Line the bottom of 9-inch round cake pan with parchment paper and coat the bottoms and sides with nonstick cooking spray or generously butter a mini bundt pan.
Whisk together flour, baking soda, salt and granulated sugar in a large mixing bowl. Add coconut oil, coconut milk, and vinegar and whisk until batter is smooth.
Pour into prepared pan. Bake for 25 to 30 minutes until a tester inserted in the center comes out batter-free. Cool the cake in the pan on a wire rack for 10 minutes, then flip it out onto a cooling rack to cool the rest of the way.
For the glaze: Whisk together 3/4 cup powdered sugar with 1 to 2 tablespoons of the leftover coconut milk, adding a little at a time, until it is smooth but not too runny. Add a pinch of salt. Once cake is fully cool, spread over the top of the cake.