Preheat your oven to 350°F (175°C) and grease and line two 9-inch round cake pans with parchment paper.

In a large mixing bowl, sift together the gluten-free baking flour, baking powder, and salt.

Using an electric mixer, beat the softened unsalted butter and granulated sugar together until light and fluffy, about 4-5 minutes.

Incorporate the eggs one at a time into the butter-sugar mixture, mixing well after each addition.

Gradually add half of the dry ingredient mixture into the wet ingredients, then add the sour cream, lemon zest, and lemon juice, followed by the remaining dry ingredients.

Gently fold in the poppy seeds into the batter.

Divide the batter evenly between the prepared pans and bake for 25-30 minutes.

Let the cakes cool in the pans for about 10 minutes, then transfer them to a wire rack to cool completely.

In a mixing bowl, beat the softened cream cheese and butter until smooth, then gradually add powdered sugar and vanilla extract.

Layer the cooled cakes with cream cheese frosting in between and on top.