Preheat your oven to 350°F (175°C). Grease 9x13 pan.
In a kitchen aid mixing bowl, combine the sourdough starter and all of the wet ingredients (coconut oil, sugar, eggs, vanilla extract, lemon zest, lemon juice, milk).
Mix on low until well combined and set aside. (Some of the coconut oil might be chunky, its ok, it will all melt in the oven).
Add the salt and baking powder.
Mix the baking soda with the vinegar, they will get foamy and then add to the mixture.
Add 2 cups of almond flour and stir with a silicone spatula. Then add 1 cup of white flour and stir.Add the poppy seeds, stir.
Pour the batter into the prepared pan and smooth the top with a spatula.
Bake in the preheated oven for 35-40 minutes, or until a toothpick inserted into the center comes out clean.
Remove the cake from the oven and let it cool in the pan for 10 minutes.
While the cake is baking make the glaze- In a small bowl, whisk together the powdered sugar and lemon juice to make the glaze.
Drizzle the glaze over the cooled cake.
Slice and serve the sourdough lemon almond poppyseed cake.