In a medium bowl, add blueberries and 1 tbsp of the flour and toss well to combine.
Preheat the oven to 350F. Butter and flour an 8-inch (20-cm) springform pan.
In a medium bowl, whisk together the dry ingredients (the remaining flour, salt, and baking powder) until combined well.
In a large bowl, add room temperature butter, coconut oil, and sugar and mix until creamy, light, and fluffy.
Add the eggs one by one and mix until combined.
Add vanilla, lemon extract, lemon juice, and lemon zest and mix well until combined.
Add the flour mixture and buttermilk to this mixture, and mix until they are completely combined. (Add them slowly; add a little flour mixture then a little buttermilk and repeat).
Add the flour-dusted blueberries, and using a wooden spoon or spatula gently fold them into the batter.
Pour the batter into the prepared pan and add some fresh blueberries on top.
Bake for about 50-60 min. (Don't forget to make a toothpick test before removing it from the oven).
Remove from the oven and cool well.
Using a mortar, mash ½ cup blueberries, and using a strainer, strain its juice.
In a small bowl, mix the powdered sugar with 3 tbsp blueberry juice (if it is too thick add one more tbsp juice until it is pourable).
Pour the glaze over the cake and serve with tea or coffee.
