Preheat oven to 350°F (180°c). Line a 12 cavity muffin pan with paper liners, or spray with non-stick cooking spray.
In a large mixing bowl combine the self rising flour, sugar and poppy seeds. Stir until well combined.
2 cups self rising flour (regular or gluten-free measure-for-measure flour blend), 1 cup granulated sugar, 2 tablespoons poppy seeds
To another mixing bowl add the milk, oil, orange juice, egg, vanilla extract and orange zest. Mix until well combined.
1 cup whole milk, 1/2 cup canola oil, 1/4 cup orange juice, 1 large egg, 1 teaspoon vanilla extract, zest from 1 orange
Pour the wet ingredients into the bowl with the dry ingredients. Stir until just combined. DO NOT OVERMIX.
Divide the batter evenly between the prepared muffin cavities (they will each be almost full to the top). Bake for 20 minutes, or until a toothpick inserted into the center comes out clean and the muffins are turning golden and cooked through. Allow to cool for 10 minutes in the muffin tin before transferring to a cooling rack. Allow to cool completely.
TO MAKE THE GLAZE: add the powdered sugar to a small bowl. Stir in 1.5 tablespoons of orange juice. You'll need just enough juice to make a glaze of drizzling consistency (you may need to use more or less than the 1.5 tablespoon of juice).
1/2 cup powdered sugar, 1.5 tablespoons orange juice
Drizzle the glaze over the cooled muffins. Allow to set for a few minutes before serving.