mixture is at room temperature; stir in the melted coconut oil, the vanilla, and the remaining orange zest.
5. add the buttermilk mixture to the flour mixture and gently stir with a rubber spatula until just blended.
6. spoon the batter into the lined muffin cups. sprinkle the orange-sugar over the tops of the muffins. bake for 17-20 minutes, or until the tops spring back when lightly touched. remove the muffins from the pan and cool on a wire rack. 