Start by preheating your oven to 350°F (175°C). Grease a 9x5-inch loaf pan with butter or non-stick spray. Alternatively, you can line the pan with parchment paper for easy removal later.

In a medium bowl, whisk together the all-purpose flour, baking soda, salt, and the optional ground cinnamon and nutmeg. This step ensures that the dry ingredients are well-combined and helps avoid clumps in your batter.

In a separate bowl, mash the ripe bananas using a fork until smooth. The ripeness of the bananas will determine how sweet the bread turns out. The riper they are, the better!

In a large mixing bowl, combine the melted butter, granulated sugar, and eggs. Beat these together until creamy. Then, add the mashed bananas and vanilla extract. Stir in the buttermilk until the mixture is smooth.

Slowly add the dry ingredients from step 2 into the wet ingredients. Mix just until combined—be careful not to overmix, as this could lead to a dense loaf.

Gently fold the cranberries into the batter. Make sure they are evenly distributed so every slice of bread gets a good amount of tartness from the cranberries. If you're using fresh cranberries, toss them lightly in flour before folding them in to prevent sinking to the bottom of the loaf.

Once the batter is well mixed, pour it into the prepared loaf pan. Smooth the top with a spatula to ensure even baking.

Place the loaf pan in the preheated oven and bake for 60 to 70 minutes. Check for doneness by inserting a toothpick into the center of the loaf—if it comes out clean or with just a few crumbs, the bread is done.

Allow the bread to cool in the pan for about 10 minutes before transferring it to a wire rack to cool completely. This step is crucial to ensure the bread sets properly and is easy to slice.