Preheat your oven to 350°F (175°C) and line or grease an 8x8-inch baking pan to prevent sticking.

In a large bowl, whisk together the melted butter and brown sugar until smooth and creamy. Add in the egg and vanilla extract, then fold in the mashed bananas until well combined.

In another bowl, whisk together the all-purpose flour, baking powder, baking soda, cinnamon, and salt until evenly mixed.

Gently fold the dry ingredients into the wet ingredient mixture until just combined, being careful not to overmix. Add chopped nuts or chocolate chips if desired.

Pour the batter into your prepared pan, spreading it evenly. Bake for 25–30 minutes, or until the edges are a light golden brown and a toothpick inserted in the center comes out mostly clean.

Allow the blondies to cool in the pan for about 15–20 minutes. Once cooled, slice them into squares and enjoy!