Adjust oven rack to lower-middle position and preheat to 350℉. Grease 8 1/2 x 4 1/2 inch loaf pan. Grind coconut sugar in coffee grinder or small food processor until fine and powder-like. Takes about 1-2 minutes.
In a large bowl, combine coconut sugar, flour, baking soda, and salt. Whisk together until well incorporated.
In a separate bowl, add the peeled bananas. Mash with a fork. Add the melted butter, eggs, yogurt, and vanilla. Whisk together well.
Add the banana mixture to the flour mixture and gently fold in until just combined working out any flour pockets. Gently fold in raspberries.
Scrape batter into prepared loaf pan. Bake until golden brown and a toothpick inserted into the middle comes out clean or a few moist crumbs about 55-65 minutes. Rotate pan halfway through baking time.
Let bread cool in pan for 10-15 minutes and remove from pan and let cool completely on a cooling rack for an hour and a half before cutting into it.