Preheat your oven to 350°F (175°C). Line an 8x8-inch baking pan with parchment paper, leaving some overhang for easy lifting. Lightly grease the paper for clean edges.

In a medium bowl, whisk together 1 cup granulated sugar and 2 large eggs until glossy and slightly thick, about 30–45 seconds. This helps the brownies set with a fudgy bite.

Add 1 cup creamy peanut butter and 1 teaspoon vanilla extract. Stir until completely smooth and no streaks remain.

Sift or whisk in 1/3 cup unsweetened cocoa powder. Fold gently until just combined. The batter will be thick—this is good. If adding chips or nuts, fold in up to 1/2 cup now.

Spread the batter evenly in the prepared pan. For tidy edges, press it into the corners with a spatula. If you like, sprinkle a pinch of flaky sea salt on top.

Bake for 20–24 minutes, or until the top looks set and a toothpick inserted near the center comes out with a few moist crumbs. Avoid overbaking.

Cool the pan on a rack for at least 30 minutes. Lift the brownies out using the parchment, slice into squares, and enjoy.