In a large bowl, combine the flour, sugar, baking powder and salt with a wire whisk. In a medium bowl, beat the milk, melted butter, egg and vanilla extract with a fork until well blended. Add the milk mixture to the the flour mixture. Also add the poppy seeds and the lemon zest. Stir until just combined (the batter will be lumpy.)

Fill the muffin-pan cups one-third full with batter. Drop a teaspoon of lemon curd on top of the batter. Top with the remaining batter. Bake until a toothpick inserted in the center of the muffin comes out clean, 20-25 minutes. Allow to cool for 1 minute, then remove muffins from pan. Allow to cool on a wire rack. Store leftovers in a sealable container.