Add the blueberries, water, and granulated sugar to a medium saucepan set over medium heat. Bring to a light boil (or heavy simmer). Mix the cornstarch with 2 tablespoons water until dissolved. Slowly stir the cornstarch mixture into the blueberry mixture. Reduce the heat to medium low and cook for about 15 minutes or until the sauce has thickened substantially. Stir in the vanilla extract and lemon juice and decrease the heat to the lowest setting possible. Keep warm until you are ready to serve.

Preheat your waffle iron.

In a large bowl, whisk together the buttermilk, whole milk, melted coconut oil, eggs, vanilla extract and lemon juice. Set aside. In another bowl, whisk together the flours, cornstarch, baking powder, brown sugar, salt, lemon zest, and poppy seeds. Add the dry ingredients to the wet and fold the ingredients together until just moistened. Set aside for about 3-5 minutes while you prepare the glaze.

Whisk the confectioner's sugar, lemon juice, milk, and salt together in a small bowl. Set aside.

Grease your waffle iron, and add about 1/4-1/3 cup of the waffle batter depending on the size of your iron. Cook until done and then repeat for the rest of your batter. Don't forget to grease your waffle iron each time you make a waffle.

To serve, drizzle the lemon glaze on top of a waffle and top with the blueberry sauce. Enjoy immediately!