Preheat the oven to 350 degrees. Line a muffin pan(s) with 20 muffin liners. In a medium mixing bowl (or 4 cup glass measuring cup), combine the wet ingredients: milk, juice, sour cream, eggs and butter. Whisk to blend. This mixture can become very lumpy if your butter is hot, so be sure to cool it a bit. You don’t want to cook your eggs!
In a very large bowl, combine the dry ingredients: flour, sugar, baking powder, and salt. Whisk to blend. Pour the wet ingredients into the dry and stir until just combined. Gently stir in the orange zest.
Fill each muffin cup 2/3 full. Bake 18-22 minutes, or until a toothpick inserted in the center comes out clean. Let cool 5-10 minutes in pan. Transfer to a wire rack placed over a baking sheet.
To make the glaze, combine all ingredients in a small bowl. Add more juice to thin glaze, if needed (or more powdered sugar to thicken). While the muffins are still warm, gently spoon or drizzle glaze over the top of each muffin. This recipe made quite a bit of glaze so I reglazed my muffins several times to enhance the orange flavor. Feel free to use as little or as much as you like! Allow the glaze to set before storing in an airtight container.