Preheat your oven to 350°F (175°C) and prepare a baking sheet with parchment paper.
In a bowl, combine the flour, baking powder, and sea salt, whisking them together until well mixed.
In a separate bowl, blend the melted coconut oil with brown sugar until creamy.
Pour in the oat milk, vanilla extract, and lemon juice, stirring until the mixture is smooth and homogenous.
Gradually incorporate the dry ingredients into the wet mixture, stirring gently until just combined.
Carefully fold in the blueberries, ensuring they remain intact.
Scoop out tablespoon-sized mounds of dough and place them on the prepared baking sheet, leaving a couple of inches between each one.
Bake for approximately 12-15 minutes, or until the cookies are golden around the edges.
Let them rest on the baking sheet for 5 minutes before moving them to a wire rack to cool completely.