In a medium bowl, mash bananas and combine greek yogurt, butter, eggs, brown truvia and vanilla extract.
On top of wet mixture, add almond flour, flaxseed, baking powder, and salt. Mix until just combined
In a separate bowl, mix together all crumble ingredients until well combined and crumble can be handled with your hands.
Grease a 9x9 pan and pour half the batter in the pan. Top with half the crumble mixture. Pour the rest of batter into pan and top with remaining crumble.
Bake at 350℉ for 50-60min or until cake doesn't jiggle in the middle when jostled.
While baking, mix together icing ingredients in small bowl. Adding Almond Milk one TBSP at a time until desired consistency is reached
Let cake cool for 10 minutes before drizzling icing and enjoying!