Preheat oven to 350°F.
Butter an 8-inch square baking pan.
Line the pan with 2 crisscrossing strips of parchment paper, buttering between each layer and leaving a 2-inch overhang on all sides.
Butter top and sides of parchment.
In a medium bowl, whisk flour, baking powder, cardamom, salt, pepper and black and white sesame seeds.
In another medium bowl, whisk brown sugar, ½ cup melted butter, eggs and vanilla until smooth.
Fold dry ingredients into wet ingredients until just incorporated, then fold in tahini until smooth.
Pour batter into prepared pan; bake 25-30 minutes until golden on the outside and center doesn’t jiggle but is still soft.
Remove from oven, cool in pan, and cut into 16 equal squares.
