Preheat the oven to 350°F (175°C). Grease and flour a 9-inch round cake pan.
In a medium bowl, whisk together the polenta, almond flour, baking powder, and salt. Set aside.
In a large mixing bowl, cream together the butter and sugar until light and fluffy.
Beat in the eggs, one at a time, incorporating each one fully before adding the next.
Add the lemon zest, lemon juice, and Greek yogurt to the batter and mix until well combined.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Pour the batter into the prepared cake pan and smooth the top with a spatula.
Bake for 35-40 minutes, or until a toothpick inserted into the center comes out clean.
While the cake is baking, prepare the glaze by whisking together the powdered sugar and lemon juice until smooth.
Once the cake is done, remove it from the oven and let it cool in the pan for 10 minutes.
Carefully invert the cake onto a wire rack and remove the pan. Allow the cake to cool completely.
Drizzle the lemon glaze over the cooled cake, allowing it to drip down the sides.
Slice and serve.