Prep the pan and oven: Preheat your oven to 350°F (175°C). Grease a 9x5-inch loaf pan and line it with a parchment sling for easy removal.

Mix the wet ingredients: In a large bowl, whisk the mashed bananas, melted butter, sugar, eggs, vanilla, lemon zest, and lemon juice until smooth and well combined.

Combine the dry ingredients: In a separate bowl, whisk together the flour, baking soda, baking powder, and salt.

Bring it together: Add the dry mixture to the wet mixture. Stir gently with a spatula just until you no longer see dry streaks. Do not overmix.

Prepare the blueberries: Toss the blueberries with 1 tablespoon of flour to help prevent sinking. Fold them gently into the batter, reserving a small handful for the top if you like.

Fill the pan: Scrape the batter into the prepared pan, smoothing the top. Sprinkle the reserved blueberries and coarse sugar over the surface for a light crunch.

Bake: Bake for 55–70 minutes, or until a toothpick inserted near the center comes out with a few moist crumbs but no wet batter. If the top browns too quickly, tent loosely with foil for the last 15 minutes.

Cool: Let the loaf cool in the pan for 15 minutes. Lift it out using the parchment and transfer to a wire rack to cool completely before slicing.

Serve: Slice with a serrated knife. Enjoy plain, or spread with butter, cream cheese, or a light lemon glaze.