Preheat your oven to 180°C (350°F). In a baking dish (about 20x28 cm), combine the oats, cinnamon, protein powder, baking soda, and salt.
In a large bowl, mash the bananas with a fork until smooth. Add the almond milk, peanut butter, yacon syrup, ground flaxseeds, and vanilla powder. Mix well and let sit for 5 minutes so the flaxseeds can thicken the mixture slightly.
Pour the wet ingredients over the oat mixture in the dish. Stir gently to ensure everything is well combined.
Bake in the preheated oven for 30 to 35 minutes, or until the top is lightly golden and the mixture has set. Remove from the oven and let cool for 5 minutes before serving.
For an extra indulgent touch, drizzle some peanut butter or add a few banana slices as a topping.