Preheat oven to 350 F, prepare the pan (9x9 inch pan) by generously coating the pan with oil and set aside.
In a large bowl, add the melted butter and melt for about 30 seconds on high heat. Next, add the granulated sugar and mix until combined. Add eggs, vanilla extract and mix until everything is just combined. (Don't overmix)
Add the unsweetened cocoa powder, all-purpose flour, salt, baking soda, and mix until well combined. Then pour the brownie batter into the pan and bake for 25-30 minutes.