Step 1: Prepare the Cake Batter

• Preheat the oven: Set the oven to 180°C (160°C fan)/350°F/gas mark 4.
• Prepare the tins: Grease and line two 20cm round cake tins with baking parchment.
• Cream the butter and sugar: In a mixing bowl, beat the softened butter and caster sugar together until light and fluffy using an electric mixer.
• Add the eggs and lemon zest: Beat in the eggs one at a time, followed by the zest of two lemons, until fully incorporated.
• Fold in the dry ingredients: Gently fold in the self-raising flour and baking powder, being careful not to overmix.

Step 2: Bake the Sponge

• Divide the batter: Evenly distribute the batter between the two prepared tins, smoothing the tops with a spatula.
• Bake: Place the tins in the preheated oven and bake for 25 minutes, or until the sponges are golden and springy to the touch.
• Cool the cakes: Allow the cakes to cool in the tins for 5 minutes before turning them out onto a wire rack to cool completely.

Step 3: Make the Lemon Buttercream

• Beat the butter: In a bowl, beat the softened butter until smooth.
• Add the icing sugar and lemon juice: Gradually add the icing sugar and lemon juice, beating until light and creamy. Stir in the zest of one lemon.

Step 4: Assemble the Cake

• Spread the buttercream: Once the sponges have cooled, spread the lemon buttercream evenly over the top of one sponge. Place the second sponge on top to create a sandwich.

Step 5: Add the Lemon Drizzle Icing

• Make the icing: In a small bowl, mix the icing sugar and lemon juice until smooth and pourable.
• Drizzle over the cake: Drizzle the lemon icing over the top of the cake, letting it gently run down the sides for a decorative finish.