Mix flour, poppy seeds, baking powder and salt together in a bowl
Whisk sugar and lemon zest in another bowl until it becomes a moist mass
Add butter and whisk until fluffy
Add eggs one at a time and whisk well between each egg
Mix milk and crème fraiche together
Add half of the flour mixture + milk mixture + lemon juice to the butter/sugar and whisk together
Add the other half and whisk until smooth
Pour the batter into a greased springform pan, 20 cm diameter (or loaf pan)
Bake the cake at 180 degrees (regular oven) for 15 minutes
If it starts to brown too much, place a piece of foil over it and bake for another 15 minutes until it is cooked through
Let it cool on a baking rack