To begin, preheat an oven to 350 and line a 9x9 pan with parchment paper, with two sides sticking out for easy cake removal.
In a small bowl, add your dry ingredients and stir them together (oat flour, baking soda, salt).
In a large mixing bowl, add your coconut oil, sugar and applesauce and whisk them together. Add in your milk, lemon juice, lemon zest, vanilla, and eggs and whisk everything together.
Now, pour your dry ingredients into your wet ingredients and stir them together till everything is well combined.
Pour your blueberries into the cake batter and gently fold them in. Pour your batter into the pan and bake in the oven for 35-40 minutes, or till the cake is springy to touch and a toothpick inserted comes out clean.
Let your cake cool, then remove from your cake pan.
Frost your cake when it's entirely cooled. Use your favorite frosting to top the cake with, cut, and enjoy!
Stored in an airtight container in the fridge, this cake will last up to 3 days.