Preheat oven to 350 degrees F. Grease or line an 8 x 8 baking pan, set aside. In a small mixing bowl combine the flour, baking soda, and salt, stir to combine and set aside.
In the bowl of a hand or stand mixer fitted with a paddle attachment, cream the butter and sugars until light and fluffy, 3-4 minutes. Add in the tahini and cream for an additional 1-2 minutes. Add in the eggs, one at a time and the vanilla. Scrap down the sides if needed.
Slowly add in the dry ingredients and mix until combined, the mixture will be fairly thick. Transfer into the prepared baking pan.
Bake at 350 degrees for 22-25 minutes or until a toothpick inserted comes out clean. Remove form the oven and let cool on a wire rack, sprinkle with flaky salt and allow to cool completely before cutting. These will keep for 4-5 days in an airtight container.