For the Cake: Grease and flour an 8-cup Bundt pan and preheat the oven to 350 degrees.
In a large bowl, combine the cake flour, 1-1/2 cups sugar, lemon zest, salt, baking powder and ground coriander.
In another bowl, mix together the milk, egg yolks, coconut oil, butter and lemon juice.
Place the egg whites in the bowl of a stand mixer fitted with a whisk attachment and whisk until they become foamy. Add the cream of tartar and continue whisking until soft peaks appear. Add the 1/2 cup sugar slowly and continue whisking until the meringue becomes stiff and shiny.
Add the milk mixture to the dry ingredients and gently combine by hand. Fold the meringue into the batter 1/3 at a time.
Transfer the batter into the prepared Bundt pan and bake for 45 minutes, rotating the pan half way through the baking time.
While the cake is baking, prepare the Coriander Syrup. The cake is done when the surface is golden and a toothpick inserted into the cake comes out with a few moist crumbs attached.For the Coriander Syrup: Heat the water and sugar in a small saucepan over medium-high heat, and stir until the sugar dissolves. Add the coriander and simmer for ten minutes, stirring occasionally. Then, pour the syrup through a fine-mesh sieve and let it cool to room temperature.For Assembly:
Cool cake for 10 minutes, and then remove it from the pan. Trim the bottom of the cake, allowing it to sit flat.
Using a long toothpick or thin skewer, poke holes into the finished cake to allow the syrup to penetrate. Then slowly pour the syrup over the warm cake.
When cool, dust with powdered sugar.