Separate the eggs yolks from whites. Set whites aside.
Mix milk with flour, sugar, cardamom, and baking powder until smooth.
Add melted butter, egg yolks, salt, and lemon zest.
Let batter rest for 5 minutes. While resting whisk the whites with a mixer until stiff peaks form.
Gently fold in whites until smooth. Do not over mix.
Put a little bit of melted butter into the wells of the heated aebleskiver pan.
Turn the batter halfway once bubbles start to form.
Slowly continue turning until a complete ball forms.