Preheat your oven to 350°F (175°C). Grease or line a 9-inch round cake pan with parchment paper.

In a large mixing bowl, combine melted butter, granulated sugar, and brown sugar.

Mix until well combined.

Add eggs one at a time, beating well after each addition.

Add vanilla extract and stir.

In a separate bowl, mix together the flour, cocoa powder, and salt.

Gradually add the dry ingredients to the wet ingredients and stir until well combined.

Be careful not to overmix.

If using, mix the chocolate chips until evenly distributed throughout the batter.

Pour the batter into the prepared cake pan and spread it out 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.

Let the cake cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.

Once cooled, slice and enjoy your delicious chocolate brownie cake.