Preheat your oven to 350°F (175°C) to ensure even baking.
Line a 9x9-inch baking pan with parchment paper, leaving overhang on the sides for easy removal.
In a large mixing bowl, whisk together melted butter and packed light brown sugar until smooth. Add pure vanilla extract and egg; mix until well combined.
In another bowl, whisk the all-purpose flour, baking powder, baking soda, and salt to evenly distribute the leavening agents.
Gradually add the dry ingredients to the wet mixture, stirring until just combined. A few lumps are okay; do not overmix.
Gently fold in the semi-sweet chocolate chips evenly throughout the batter.
Pour the batter into the prepared baking pan and spread evenly with a spatula. Bake for 20-25 minutes until the top is golden and a toothpick inserted comes out with a few moist crumbs.
Allow the blondies to cool in the pan for 10 minutes before lifting out with the parchment paper. Cool completely on a wire rack before cutting into squares and serving.