Preheat the oven to 350 degrees F. Rub coconut oil on two 9-inch round cake pans and line the bottoms with parchment paper. Put a bit more coconut oil on the parchment paper and dust it with flour.
Whisk the flour, baking powder and salt in a bowl until well combined. Fold in coconut. In a separate bowl, beat the coconut oil and sugar together until well incorporated. Add in the eggs, one at a time with the beater on medium speed, scraping down the bowl as needed. Add in the vanilla. In a small bowl combine the milk and lemon juice.
Beat in the flour mixture in 3 batches, alternating with the milk and lemon juice mixture, beginning and ending with flour, until just smooth. Divide the batter into the two pans and bake for about 35-40 minutes or until the cakes are golden brown and an inserted toothpick comes out clean. In the meantime make the icing by whisking together all icing ingredients (you want the icing to be pretty thick, it’s too thin add more powdered sugar and if it’s too thick add more lemon juice). Set aside.
Once cooked, remove cake pans from the oven and place pans onto a cooling rack and allow to cool for 10 minutes, then remove cakes and allow to continue to cool. Pour half of the icing onto the bottom layer of the cake and spread around. Place the top half on top and ice again. Garnish with lemon slices.