In a medium mixing bowl, combine the all-purpose flour, baking powder, baking soda and salt. Set aside.
In a large bowl, using a hand-mixer, beat together the tahini and softened butter until very smooth, about 30 seconds. Add the two sugars and beat once more until smooth, about 30 seconds. Next, beat in the egg and vanilla extract. In two batches, add the dry ingredients until no speckles of flour are visible. The dough should be soft and supple. Transfer to the fridge to chill for about 10 minutes.
Meanwhile, preheat the oven to 350 degrees. Line a baking sheet with parchment and set aside. To a small bowl, combine the sesame seeds and sugar.
Using a 2-ounce cookie dough scooper (or a tablespoon), scoop out a ball of dough. Roll the dough into a circle using the palm of your hands. Roll the ball of dough in the sesame/sugar mixture until it's completely covered. Transfer to the cookie sheet; repeat the scooping and rolling process until you've worked through about half the dough (you'll need to bake these cookies in two batches), being sure to space the cookies about 3-inches apart (they'll spread a bit).
Transfer to the oven and bake for 10 minutes, until the cookies have spread slightly. Carefully remove the baking sheet from the oven and using the opposite end of a spatula, make an indentation in the center of the cookie. If the hole isn't big enough you might have to make a crater using a few taps with the edge of the spatula. Return the cookies to the oven and bake for an additional 5 minutes more, and until the edges are lightly golden brown. Allow to cool for 5 minutes on the baking sheet (they'll be very fragile right when they come out of the oven) and then transfer them to a cooling rack until they're room temperature. When cooled, add a teaspoon of jam to the center of the cookies. These cookies will keep in an airtight container for up to 5 days.