In the bowl of an electric mixer, cream the butter and sugar until light. Add the eggs and continue to beat until well blended. Add the flour, baking powder, toasted sesame seeds, orange peel, and raisins; blend until combined.
Seal the dough airtight in plastic wrap. Refrigerate until firm, overnight, if desired. (The longer chilling allows the fruit peel flavor to permeate the dough.)
Divide the dough into 4 equal pieces. Roll each piece into a smooth even log 1inch thick. Roll each log in the untoasted sesame seeds until coated.
Preheat the oven to 350°F. Move an oven rack to the middle position. Line 2 large baking sheets with parchment paper.
Place 2 of the logs, spaced 5inches apart, lengthwise on each baking sheet.
One sheet at a time, bake the logs until golden, about 20 minutes, turning the sheet midway.
Remove the first sheet from the oven and set aside on a wire rack to cool for 10 minutes. Then, while the logs are still warm, slice them crosswise into cookies a scant ¼inch thick. Place the cookies on their sides, ¼inch apart. (While you are slicing the first logs, you can bake the remaining 2 logs.)
Return the sliced cookies to the oven and bake until lightly golden, 7 to 10 minutes. Cool on the baking sheets set on wire racks.