Preheat the oven to 180°C. Grease a bundt pan (only if it’s not silicon).
Sift the flour and baking powder into a bowl.
In a large mixing bowl, whisk the eggs, sugar, salt and butter until light and fluffy. Add the kefir, lemon zest & juice and mix. Add the flour while mixing gently. Fold in the poppy seeds and combine. The batter should be smooth and not too thick.
Spread the batter evenly into the pan.
Bake the cake for about 40 minutes in the middle of the oven or until a skewer inserted in the centre comes out clean. (If the cake looks already golden after 20 minutes, cover the top loosely with aluminium foil)
Let the cake cool for 5 minutes in the tin, then turn it out onto a wire rack.
While the cake is cooling down, prepare the glaze by combining the lemon juice and caster sugar. Drizzle the mixture over the warm cake.
When the cake has completely cooled down, (but the glaze is still sticky), sprinkle the top with more caster sugar.