Preheat the oven to 200 degrees and grease and line 2 x muffins trays with paper cases (mixture makes approximately 18).
Place the butter and ⅔ of a cup of orange marmalade in a small saucepan and stir over a low heat until combined. Set aside for a couple of minutes to cool slightly.
Sift the flour into a large bowl and stir in the poppy seeds and sugar, making a well in the centre.
Whisk together the milk, eggs and rind in a jug and pour into the well. Then add the melted butter and marmalade mixture and fold gently to combine (using a metal spoon).
Spoon mixture into paper cases, until approximately ¾ full. Bake in oven for 15 minutes, or until golden on top and cooked through when tested.
While muffins are cooking, heat remaining marmalade and then push it through a sieve. When muffins are out of the oven, brush the tops generously with the warm marmalade and allow to cool in tray for 10 minutes before transferring to a wire rack to cool completely.