Preheat your Belgian waffle iron and spray it with non-stick cooking spray. Set it aside.
Carefully separate the egg yolks and egg whites and put them in 2 separate medium-sized bowls.
Combine all dry ingredients (flour, baking powder, salt, sugar, cinnamon, protein powder) in a third medium bowl. Use a whisk to make the job easier.
Beat the egg whites, either by whisk or by a hand mixer, until stiff peaks form and set it aside.
In your bowl that has egg yolks, add all remaining ingredients (oil, yogurt, milk) into it and mix them together. Then, pour the wet mixture in the bowl of the dry ingredients and mix everything together.
Fold the egg whites into your mixture. Do not mix too much or too fast. You should have a nice, thick batter in your bowl after this step.
Pour your batter into your preheated waffle iron and let them cook until they turn solid and golden-brown.
If there is more batter left after the waffles finish cooking, repeat the previous step until all the batter is finished.
Once done, serve the waffles on a dish and add your favorite toppings.