• Preheat the oven to 220C (or 425F) and generously grease a 12 cup muffin baking pan with butter or oil.
• In a large bowl, sift the flour, baking powder, baking soda, salt , sugar and cinnamon together. Add coconut and whisk well to combine. Set aside.
• In a medium bowl, combine the oil, eggs, milk and lemon juice mixture and vanilla and stir to combine.
• Make a well in the center of the dry mixture and add the wet ingredients. Gently fold the mixture until just combined (about 9 folds) and then gently fold the feijoas in until just incorporated.
• Evenly divide the batter into the 12 muffin cups, making sure that the mixture is topped to the brim (tip: using an ice cream scoop can help ensure even amounts of mixture in each muffin cup).
• Bake for 5 minutes at 220C (425F), then reduce the heat to 190C (375F) and bake for another 15 minutes or until a toothpick inserted into the center comes out clean.
• Cool muffins for 5 minutes before inverting onto a cooling wrack and drizzle feijoa glaze over top.

To make glaze

• In a small bowl, add feijoa juice, icing sugar and meltled butter until completely combined. Using a spoon, drizzle the glaze over the muffins.