In a microwave-safe, large bowl, melt the butter and then add the sugar, cocoa, salt and espresso powder. Cream together until smooth.
Mix in the vanilla extract, water and the eggs until combined.
Mix in the oat flour and baking powder (for the cakey brownie version).
Line an 9x9 inch square pan (8x8 will be too small) with parchment paper or a silicone liner and pour the batter evenly it.
Bake for 25-30 minutes until the tops of the brownies appear just set and a toothpick inserted in the center comes out with just a few moist crumbs.
Place the baking pan on a wire rack and allow to cool completely, at least 2 hours (the hardest part!). This is imperative so that they hold their shape.
Use the parchment/silicone to lift the cooled brownies onto a cutting board. Using a clean, sharp knife, cut the brownies into bars, cleaning the knife between cuts.
Enjoy!
Notes
LeftoversStore leftover brownies in an airtight container at room temperature for up to 4 days, in the refrigerator for up to 1 week or freeze for up to 3 months.*Nutrition calculated based on fudgy version.