Preheat oven to 170°C and grease a bundt cake tin then dust it with flour.
Mix the flour, baking powder, baking soda and poppy seeds.
Beat the butter until smooth and creamy. Add the sugar, vanilla and lemon zest, then mix well until creamy.
Add a spoonful of the flour mixture then one egg. Combine well then repeat this - alternating the flour and the egg.
Finally add the soured cream and lemon juice and gently combine. Do not overmix!
Spoon the batter into the tin then smooth the top with a spatula, making sure the batter has spread out evenly.
Bake for 50 mins or until a skewer inserted into the centre comes out dry.
Place the cake on a wire rack to cool for 10 mins then turn it out.
Cool completely while you make the glaze: Mix together the lemon juice and powdered sugar then add a few drops of water to make double cream consistency.
Drizzle this over the cake and let it set before serving.