Position oven rack in lower third of oven. Preheat to 325°F.

Line an 8-inch square pan with parchment paper and lightly grease.

In a large glass bowl, combine butter, coconut sugar, cocoa powder, and salt.

Set bowl over a small pot of simmering water and stir until butter melts and mixture is smooth. Remove from heat and cool for 5–10 minutes.

Stir in vanilla extract and vanilla bean paste.

Add eggs and beat vigorously until glossy and well combined.

In a separate bowl, mix flour and baking powder. Stir into the batter until fully incorporated.

In a small bowl, combine powdered peanut butter and water until smooth.

Pour brownie batter into prepared pan. Drizzle peanut butter mixture over top and use a knife to swirl.

Bake for ~35 minutes, until a tester comes out with moist crumbs.

Cool completely on a wire rack before cutting.