Preheat your oven to 180°C (350°F)
Peel and mash the 4 ripe bananas in a separate bowl using a fork until smooth. The riper, the better, as this enhances the sweetness.
In another large mixing bowl, add the mashed bananas and 3 eggs. Mix gently until just combined. Avoid overmixing to keep the texture light and fluffy.
Add the quark or Greek yogurt into the mixture. Stir until smooth.
Add 1 tablespoon of vanilla aroma and 2 tablespoons of cinnamon to the mixture. Adjust cinnamon to your taste for the perfect level of warmth and spice.
Gradually sift in 150 grams of oat flour and 1.5 tablespoons of baking powder. Stir gently to incorporate.
Add 30 grams of your favorite protein powder (vanilla works well) and mix until the batter is smooth and evenly combined.
Fold in or sprinkle on your favorite toppings, such as pure chocolate chips or chopped nuts, for added texture and flavor.
Line a loaf pan with parchment paper or grease it lightly to prevent sticking. Pour the batter into the pan and spread it evenly.
Bake the banana bread for 30–35 minutes, or until a toothpick inserted into the center comes out clean.
Let the banana bread cool in the pan for about 15 minutes before transferring it to a wire rack. Slice into pieces and enjoy!