Get Ready to Bake: Preheat your oven to 350°F (175°C) and lightly grease your donut pan with non-stick spray.
Mix Wet Ingredients: In a spacious bowl, gently whisk together the berry puree, eggs, vanilla extract, lemon zest, and almond milk until smooth and well combined.
Combine Dry Ingredients: In a separate bowl, stir together the almond flour, oat flour, protein powder, monk fruit granulated sweetener, baking powder, and a pinch of salt.
Create the Batter: Gradually add the dry ingredient mixture into the wet ingredients, stirring just until everything is combined and you have a thick, fragrant batter. Be careful not to overmix!
Fill the Pan: Carefully spoon or pipe the donut batter into each cavity of your prepared donut pan, filling them almost to the top.
Bake to Perfection: Pop the donut pan into the preheated oven and bake for about 12-14 minutes, or until the donuts are golden around the edges and firm to the touch.
Cool Down: Let the donuts cool in the pan for a few minutes before gently transferring them to a wire rack to cool completely.
Whip up the Glaze: While the donuts cool, whisk together the powdered monk fruit sweetener and lemon juice in a small bowl until you achieve a smooth, pourable glaze consistency. Add a tiny bit more lemon juice if it's too thick, or a pinch more sweetener if too thin.
Glaze and Enjoy: Once the donuts are fully cooled, drizzle them generously with the lemon glaze. Let the glaze set for a few minutes before serving.