Set your oven to 350°F (177°C) and grease a 4 x 8-inch loaf pan thoroughly with nonstick cooking spray. Ensure the oven rack sits in the exact center position to encourage even heat distribution around the pan.

Place the peeled ripe bananas into a spacious mixing bowl and crush them thoroughly with a fork or potato masher. Look for a glossy, speckled puree that retains only tiny, soft pieces of fruit throughout.

Scatter the baking soda directly over the mashed fruit and stir gently to combine. Watch for a slight foaming action across the surface as the leavening reacts with the natural fruit acids.

Pour the melted unsalted butter into the bowl and stir until fully integrated. The mixture will turn glossy, smooth, and golden with an even emulsion.

Add the granulated sugar, salt, beaten eggs, and pure vanilla extract, whisking until uniform. Stir until the sugar begins to dissolve and the liquid takes on a smooth, pale amber sheen.

Fold in the gluten-free all-purpose flour and additional xanthan gum if needed, stirring just until no dry streaks remain. The final batter should look thick, smooth, and ribbon-like without overworking the starch base.

Transfer the prepared batter into the greased loaf pan, smoothing the top surface gently with a silicone spatula. Spread the batter evenly into the corners so the loaf rises with a balanced, attractive center crown.

Bake on the center oven rack for 50 to 60 minutes until golden brown and set. A wooden toothpick inserted into the thickest part of the center dome should emerge clean or with a few dry crumbs.

Transfer the pan to a wire cooling rack for ten minutes, then turn the loaf out onto the rack to cool completely before slicing. Allowing the loaf to reach room temperature lets the internal starches stabilize for clean, intact slices.