Preheat your oven to 350°F (175°C) and line a 9×13-inch (23x33cm) baking pan with parchment paper, allowing some overhang on the sides for easy removal.

In a large mixing bowl, combine the melted butter and granulated sugar, whisking together until smooth and well combined.

Add the eggs and vanilla extract to the butter mixture. Whisk vigorously until the mixture becomes light and fluffy.

In another bowl, whisk together the flour, cocoa powder, salt, and baking powder. Gently fold this dry mixture into the wet ingredients until just combined.

Pour the brownie batter into the prepared baking pan, spreading it evenly. Bake in the preheated oven for 25-30 minutes or until a toothpick inserted into the center comes out with a few moist crumbs.

While the brownies are baking, prepare the tiramisu layer. In a shallow dish, mix the brewed coffee and coffee liqueur (if using). This will be used for soaking.

In a medium bowl, whisk together the mascarpone cheese, powdered sugar, and vanilla extract until smooth and creamy.

Once the brownies are out of the oven, allow them to cool in the pan for about 10 minutes. Poke holes over the surface with a toothpick.

Carefully pour the coffee mixture over the warm brownies, allowing it to soak in.

Spread the mascarpone mixture evenly over the top of the soaked brownies. Dust with cocoa powder for a finishing touch.

Refrigerate the brownies for at least 2 hours before slicing.