Preheat oven to 350°F. Spray a 9x5 loaf pan with non-stick spray. Set aside.
In the bowl of an electric mixer, beat together bananas, yogurt, peanut butter, butter, eggs, and vanilla extract for 1 minute. Add sugar and brown sugar. Beat until completely combined {about 1 minute}.
In a medium bowl, whisk together flour, flaxseed meal, baking soda, salt, cinnamon, and allspice.
With the mixer off, add half of the flour mixture to the banana mixture. Beat about 20 seconds on low and add remaining flour mixture. Beat until just combined, making sure flour is completely incorporated.
Transfer batter to the prepared loaf pan, and bake in a preheated oven for 50-60 minutes until a cake tester or toothpick inserted into the center comes out clean. If the top starts to brown too much, cover loosely with foil.
Let cool in pan for 10 minutes before transferring to a cooling rack to cool completely.