Preheat oven to 350° and grease a 11 x 17" baking dish or line with parchment paper.
In a large bowl, beat the butter and sugar until smooth and creamy. Stir in the egg and vanilla.
In a separate bowl, mix together the flour, baking powder, and salt. Gradually add the dry ingredients to the creamed mixture until fully combined. Divide the dough into 4 portions.
Using your hands, shape each portion into a 10 x 2 1/2" rectangle on the cookie sheet. All four fit well on an 11 x 17" or bake in batches on smaller sheet. Use a finger to make a 1/2" indentation down the center of each portion. Bake for 10 minutes.
Meanwhile, place the jam into a ziplock bag and snip the tip. Remove the cookies from the oven. Pipe the jam down the center, then bake for another 10 - 15 minutes, or until lightly browned.
Cool for 3 minutes, then one at a time, move each portion to a cutting board. Cut into 1/2 - 3/4" ribbons. Place on wire rack to cool completely. Enjoy!
Notes
For added sweetness, add a glaze: 1 cup powdered sugar, 1 - 2 tablespoons milk, 1/2 teaspoon vanilla extract, and (optional) 1/2 teaspoon fresh lemon zest. Mix ingredients until smooth, then drizzle over Raspberry Ribbon Cookies.