Preheat your oven to 350°F / 175°C and position an oven rack in the center.
Grease an 8x8 inch / 20x20 cm brownie pan with butter or cooking spray, or line it with parchment paper for easy removal.
Add all —pecans, dried apples, water, softened butter, vanilla, cinnamon, erythritol, baking powder, and ground flax seed—into a high-speed blender.
Blend on high for 30–60 seconds until the batter is completely smooth, with no large chunks of pecans or apples remaining.
Pour the batter into your prepared pan and use a spatula to smooth the top.
Bake for 45 minutes, or until the center is set and the edges are pulling away from the sides of the pan.
Remove from the oven and let the bars cool completely in the pan for at least 20–30 minutes before slicing. This step is crucial for them to firm up.