Preheat oven to 400 degrees F. Grease a 12 cup muffin pan or line with paper cups.

Melt 1/2 cup of butter and set aside to cool.

In a large bowl, zest the orange (juice it as well, and set the juice aside for later) and add sugar. Using your hands, rub the orange zest and sugar together until well blended and fragrant. Add flour, baking powder, baking soda, salt and poppy seeds. Mix until well blended.

In a separate bowl, whisk together sour cream, eggs, vanilla, fresh -squeezed orange juice (reserve 3 Tablespoons of it for the glaze), and melted butter until well mixed. Pour liquid mixture over the dry ingredients. Gently stir until just combined. Do not over mix, a few lumps are fine.

Spoon into your prepared muffin pan. Bake at 400 degrees F for 15 – 18 minutes, or until golden brown and cake tester comes out clean.

While the muffins are baking, make the glaze by whisking together the powdered sugar and 3 tablespoons orange juice until smooth.

Remove muffins from pan, place on a cooling rack with a cookie sheet beneath to catch the over spill. Allow to cool for a few minutes before drizzling the glaze over muffins.