In a large bowl, mash together bananas, eggs, butter, truvia, butter, and vanilla until well combined
Add in flour, flaxseed, baking powder, and salt. Mix until just combined.
In a separate bowl, mix together all filling ingredients until smooth.
Prep a 9x5 loaf pan with parchment paper and nonstick spray. Pour half of the batter in the bottom of the pan. Then pour half of the filling on top of the batter. Pour the rest of the batter and the rest of the filling into the loaf pan.
Bake at 350℉ for 50-55min.
Let cool slightly, slice, and enjoy!