Preheat oven to 350ºF.
Sift together flour, cocoa, salt, baking soda, and sugar.
Create a well in the dry ingredients and add the olive oil, vinegar, vanilla, and water.
Whisk until combined.
Pour into a greased 9x13 baking pan.
Dot the surface with the peanut butter. Swirl in the peanut butter.
Bake for 40-45 minutes or until a toothpick comes out clean.
