Preheat your oven to 350°F and line a baking sheet with parchment paper.
In a large bowl, combine the tahini, granulated erythritol, egg, vanilla extract, baking soda, and salt. Stir with a spatula until everything is fully combined and a smooth, thick dough forms.
Refrigerate the dough for 15 minutes. This step is essential because tahini dough is naturally soft, and chilling it makes scooping and shaping much easier.
While the dough chills, spread the sesame seeds on a small plate and set it nearby for rolling. Scoop rounded tablespoons of the chilled dough and roll each one into a smooth ball. Roll each ball in the sesame seeds, pressing gently so they stick to the surface.
Place the cookies on the prepared baking sheet about 2 inches apart. Press each one down gently with the back of a fork to create a crosshatch pattern, then sprinkle each cookie with a pinch of flaky sea salt.
Bake for 10-12 minutes until the edges are golden and the centers look just set. Let the cookies cool on the baking sheet for at least 10 minutes, as they firm up significantly and develop a perfectly chewy texture as they rest.
