Preheat oven to 350°F (175°C) and grease an 8x8 inch square baking pan or line with parchment paper.
In a large mixing bowl, whisk together the melted butter and brown sugar until smooth.
Add the egg and vanilla extract, whisking vigorously until the mixture is glossy and well combined.
Fold in the gluten-free flour blend, salt, and baking powder using a spatula until just incorporated.
Fold in the chocolate chips.
Spread the batter evenly into the prepared baking pan.
Bake for 20 to 25 minutes, or until the edges are golden brown and a toothpick inserted into the center comes out with a few moist crumbs.
Allow the blondies to cool completely in the pan on a wire rack before slicing into 16 squares.