Preheat your oven to 180°C (350°F)
In a large bowl, rub the caster sugar and lemon zest, then add the egg, vegetable oil, milk, vanilla bourbon paste, Labneh and lemon juice
Whisk in the flour, baking powder, baking soda, and salt
Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Gently fold in the raspberries
Pour half the batter into a small loaf tin (8x4-inch). Spread the lemon curd evenly over the batter and swirl into the cake, pour the remaining batter on top, then add remaining lemon curd
Pipe vanilla butter down the middle of the cake. Scatter remaining raspberries on the surface if desired
Bake for 40–45 minutes, or until a knife inserted into the center comes out clean. Cover the loaf with foil after 20 minutes of baking to prevent raspberries from burning
Let the cake cool in the tin for 10 minutes, then transfer it to a wire rack to cool completely
In a small bowl, mix the icing sugar and lemon juice until smooth. Adjust the consistency by adding more lemon juice to thin or more sugar to thicken
