Preheat your oven to 350°F (175°C) and prepare a 9x9-inch baking pan by greasing it lightly or lining it with parchment paper for easy removal.
In a large mixing bowl, sift together the unsweetened cocoa powder and zero-calorie sweetener. Mix well until both components are fully combined.
Incorporate the unsweetened applesauce, Greek yogurt, large eggs, and pure vanilla extract into the dry ingredients. Using a whisk, blend until the mixture reaches a smooth, creamy consistency.
In a separate bowl, whisk together the whole wheat flour, baking powder, and salt to ensure even distribution of the leavening agent.
Gradually fold the dry ingredient mixture into the wet ingredients, mixing gently. Stir until just combined; be cautious not to overmix as this can affect the texture of the brownies.
Carefully fold in the dark chocolate chips, distributing them evenly throughout the batter for a delightful burst of chocolate in every bite.
Pour the batter into the prepped baking pan. Use a spatula to spread it evenly across the surface, ensuring a level layer for even baking.
Place the pan in the preheated oven and bake for 25-30 minutes. To check for doneness, insert a toothpick into the center; it should come out clean or with a few moist crumbs attached.
Once baked, remove the brownies from the oven and allow them to cool in the pan for 10 minutes. After this, transfer them to a wire rack to cool completely, ensuring they firm up nicely.
Once cooled, cut the brownies into squares for serving and enjoy!
Notes
For an appealing touch, lightly dust the brownies with cocoa powder or top them with fresh berries.