Prep the pan: Preheat oven to 350°F (175°C). Grease a 9x9-inch pan and line with parchment paper.
Make the brownie batter: Melt butter in a saucepan. Remove from heat and mix in sugar. Add eggs one at a time, then vanilla. Sift in flour, cocoa powder, and salt. Stir gently until combined.
Prepare the halva layer: In a bowl, crumble tahini halva. Mix with black sesame seeds, honey, and vanilla to form a thick paste.
Layer the brownie and halva: Pour half the brownie batter into the pan. Add spoonfuls of halva mixture on top and swirl lightly. Pour remaining brownie batter over halva layer.
Bake: Bake for 30–35 minutes. Toothpick should come out with a few moist crumbs.
Cool and serve: Let cool 15 minutes, slice, and sprinkle extra black sesame seeds on top.