Step 1

Stir the powdered sugar, peanut butter, melted butter, and salt together in a medium bowl.

Step 2

Preheat the oven to 325 degrees F, mist a 9x9-inch pan with non-stick spray, and line it with parchment.

Step 3

Place the sugar, melted butter, cocoa, and salt in a large bowl and stir together until combined.

Step 4

Stir in the eggs.

Step 5

Add the flour and baking powder, and mix until smooth.

Step 6

Stir in the vanilla, then pour half the batter into the prepared pan.

Step 7

Drop about half the peanut butter swirl mixture in dollops over the surface of the brownie batter. Swirl with the tip of a knife.

Step 8

Layer the remaining brownie batter on top, and repeat the peanut butter swirl.

Step 9

Bake for 45 to 60 minutes, or until set around the edges but still soft towards the center.

Step 10

Cool completely in the pan, then transfer to a cutting board and cut into squares.