Preheat the oven to 350F
In a bowl, whisk all the dry ingredients and set them aside
In a large bowl, put the room temperature coconut oil, butter, and sugar and mix until light and fluffy
Add the eggs one by one and mix
Add vanilla, lemon zest, and lemon juice and mix until well 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)
Mix 1 tbsp flour with the blueberries, add them to the cake mixture and mix gently
Pour the cake mixture into a prepared pan
Bake for about 60 minutes (perform toothpick test)
Remove from the oven and cool well
Serve the cake with blueberry icing glaze or powdered sugar