Why does adding lemon juice before baking cause a thick layer of dense cake to form? I am trying to adapt a recipe for lemon cake. I want to add actual lemon juice to the batter and omit the lemon zest. The recipe I have goes as follows:


250g butter 
250g sugar, half and half powdered and granular 
4 separated eggs 
250g flour 
baking powder for 250g flour 
zest of 2 1/2 lemons


I experimented with several ratios of lemon juice to the other ingredients. However, each time I tried it, when I took the cake out of the oven and looked at the cross section there was a dense, slightly darker layer at the bottom which disrupts the otherwise fluffy nature of the cake.

How can I get rid of this layer, while still adding lemon juice to the cake?
The original recipe is leavened with baking powder, which these days is a mixture of baking soda, an acid, and a special acid which activates at high temperatures.

Lemon juice is strongly acidic, and will react with all the baking soda in the baking powder. This means you won't get as strong a leavening effect during baking. (Some people also feel that the un-reacted acid from the baking powder results in a metallic taste.)

To compensate for this, you can try adding baking soda (in addition to the baking powder) to the recipe; I've heard 1/2 tsp baking soda to 1 tbsp lemon juice, but I don't have any direct experience with that. I don't know what this will do to the overall leavening or taste of the cake.

It is unusual to see lemon cake recipes which use much lemon juice in the batter. Drizzling lemony syrup in afterwards is more common. You might want to try that instead.