Preheat your oven to 350°F. Grease a muffin pan or a 9 x 5 inch loaf pan lined with parchment paper to ensure easy removal after baking.
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt.
In a standing mixer or a bowl with a hand mixer, beat the butter until light and creamy, about 60 seconds.
Add the sugar and continue beating for about 2 minutes until light and fluffy.
Add the eggs one at a time, mixing well after each addition. Then add the vanilla extract and beat for 1 minute until combined.
Alternately add the flour mixture, passionfruit pulp, and Greek yogurt into the batter until well combined.
Pour the batter into the prepared muffin cups or loaf pan, filling them two-thirds full.
Bake in the preheated oven for 14 to 15 minutes for muffins or about 45 minutes for a loaf, until a toothpick comes out clean.
Allow the muffins to cool for 1 hour in the pan before transferring them to a wire rack to cool completely.
For the glaze, combine passionfruit juice and seeds with powdered sugar. Add a tablespoon at a time of milk to reach desired consistency.
Drizzle the glaze over the cooled muffins or loaf and serve.
