Preheat oven to 375 degrees Fahrenheit. Prepare a 6-inch round pan.

Sift the flour, sugar, almond flour, baking powder, baking soda, and salt in a mixing bowl. Whisk well to combine.

In another bowl, combine the oat milk, sunflower oil, lemon zest, and lemon juice. Pour the wet mixture into the dry mixture and use a spatula to gently mix together. Don’t over-mix. The batter should be a bit lumpy.

Pour the batter into the prepared pan and spread evenly. Bake for about 35 minutes, until a toothpick inserted into the center of the cake comes out clean. Let cool in the pan for 10 minutes, then turn out on a wire rack to cool completely.

To make the icing, whisk the powdered sugar and lemon juice together until smooth and drizzle over the fully cooled cake.