Preheat oven to 350 degrees F. Spray a 9x5" loaf pan with non-stick spray.
In a large bowl, mash bananas with a whisk. Add yogurt, peanut butter, oil and eggs and whisk until fairly smooth. Add sugars and whisk until combined.
Add flour, flax, baking soda and cinnamon and stir just until combined, being careful not to overmix.
Spread half of the batter in the bottom of the loaf pan. Spoon half of the jam over the batter in teaspoonfuls and swirl gently with a knife. Top with remaining batter and swirl remaining jam on top of that.
Bake for 25 minutes until top is golden brown and then cover with a piece of tin foil sprayed with non-stick spray. Bake another 20-25 minutes or until a toothpick comes out clean.
For the glaze, heat jam and milk in a small bowl in the microwave until liquid. Stir in icing sugar with a whisk and drizzle over bread.