Heat the oven to 175 C / 350 F. Line two sheet pans (33 x 46 cm / 13 x 18 inch) with parchment paper.

In a large bowl, whisk the tahini, granulated sugar, and brown sugar together until smooth, about 1 minute.

Add the egg, lemon zest, lemon juice, and vanilla. Whisk until fully combined and slightly lighter in color.

In a separate bowl, mix the flour, baking soda, baking powder, and salt.

Fold the dry ingredients into the tahini mixture until a soft dough forms. It will feel slightly sticky, that's normal.

Cover the bowl and chill the dough for 30 minutes, until firm enough to roll. Skipping this step makes the cookies spread too thin in the oven.

Scoop the dough into 25 g portions, about 1.5 tbsp each, and roll into balls.

Roll each ball in sesame seeds, pressing gently so the seeds stick all over the surface.

Place the balls 5 cm apart on the prepared sheet pans, then flatten each one slightly with your palm to about 1 cm thick.

Bake one sheet at a time for 11 to 13 minutes, until the edges turn golden and the centers still look a little soft.

Cool the cookies on the pan for 5 minutes, then move them to a wire rack to cool completely.