Preheat your oven to 350 degrees. Line an 8x8 inch baking pan with parchment paper, allowing some overhang for easy removal of the brownies later.

In a microwave-safe bowl, combine the dark chocolate and butter. Heat in the microwave in 30-second increments, stirring after each one, until the chocolate and butter are fully melted and smooth. Stir in the espresso powder.

In a large bowl, whisk together the eggs, sugar, and vanilla extract until smooth.

Gradually pour the melted chocolate mixture into the egg mixture, whisking constantly to combine. Ensure the mixture is fully incorporated.

Stir in the salt and the grated, well-drained zucchini.

In a separate bowl, whisk together the gluten-free flour blend and cocoa powder. Gradually add this dry mixture to the wet ingredients, stirring until just combined.

Pour the brownie batter into the prepared baking pan, spreading it out evenly.

Bake for 25-30 minutes, or until a toothpick inserted into the center of the brownies comes out with a few moist crumbs.

Allow the brownies to cool completely in the pan placed on a wire rack.

Once cooled, use the parchment paper to lift the brownies out of the pan. Cut into squares and serve.