Preheat the oven to 350°F (175°C).

Grease your 9x9 inch baking pan or line it with parchment paper.

In a mixing bowl, whisk together the flour, sugar, cocoa powder, baking powder, and salt.

In a separate bowl, mix the vegetable oil, water, and vanilla extract.

Pour the wet mixture into the dry ingredients and stir until just combined.

If desired, fold in chocolate chips or nuts.

Spread the brownie batter evenly into the prepared pan.

Bake in the preheated oven for 25 minutes or until a toothpick inserted in the center comes out with a few moist crumbs.

Let the brownies cool completely in the pan before cutting.