Heat the oven to 350°F (175°C). Grease a 9 x 5-inch loaf pan and line it with parchment paper if desired, leaving some paper hanging over the long sides for easy removal.

Cream the softened butter and granulated sugar in a large mixing bowl until the mixture looks light and smooth. This usually takes a few minutes with an electric mixer, though a sturdy wooden spoon also works.

Beat in the eggs one at a time, mixing after each addition. Stir in the vanilla extract, then add the mashed bananas and mix until evenly combined.

In a separate bowl, whisk together the all-purpose flour, baking soda, and salt. This distributes the leavening and salt throughout the flour before it reaches the wet ingredients.

Add the dry ingredients to the banana mixture and stir just until no dry streaks remain. Do not overmix, because too much stirring can make the finished loaf dense.

Pat the diced strawberries dry with paper towels, then gently fold them into the batter. Use a light touch so the berries stay in pieces rather than breaking down and adding excess liquid.

Transfer the batter to the prepared loaf pan and spread the top into an even layer. Place the pan in the center of the preheated oven.

Bake for 55–65 minutes, checking near the end of the baking window. The bread is ready when a toothpick inserted in the center comes out clean or with a few moist crumbs.

Let the loaf cool in the pan for about 15 minutes, then lift it out using the parchment or carefully turn it onto a rack. Cool completely before slicing so the crumb can set properly.