Preheat your oven to 350°F (175°C) and lightly grease a 9-inch round cake pan or line it with parchment paper.

In a large mixing bowl, combine oat flour, whey protein powder, almond flour, baking powder, baking soda, and salt. Mix well to ensure no lumps remain.

In a separate bowl, whisk together almond milk, Greek yogurt, eggs, honey (or maple syrup), and vanilla extract until smooth.

Gradually add the wet ingredients to the dry ingredients, stirring until a smooth batter forms. Avoid overmixing.

Pour approximately 3/4 of the batter into the prepared cake pan, spreading it evenly.

In a small bowl, mix the cocoa powder with 1-2 tablespoons of water to create a thick but pipeable paste. Add more water if needed for consistency.

Transfer the cocoa mixture to a piping bag or a small zip-top bag with the corner snipped off.

Using the piping bag, create small dots or patterns on the surface of the batter in the pan.

Carefully spoon the remaining batter over the cocoa dots to lightly cover them, ensuring they don't smear. Smooth the top gently with a spatula.

Bake the cake in the preheated oven for 25-30 minutes, or until a toothpick inserted into the center comes out clean.

Allow the cake to cool in the pan for 10 minutes, then transfer it to a wire rack to cool completely before slicing and serving.