In a microwave-safe bowl, combine butter, cream cheese, and coconut oil, and melt in 30-second increments.
Next, add in 4 eggs and beat for 1-2 minutes. Then add in vanilla extract, juice of 1 lemon, and lemon zest.
Mix all dry ingredients in a bowl and then mix into the wet batter.
Fold in blueberries, being careful not to smash them.
Divide the batter among 12 muffin tins. Cook for 20-30 minutes until the tops of muffins are golden and a toothpick inserted is clean. Let cool completely before icing.
In a medium bowl, add confectionary sugar, juice of 1 lemon, and mix.