Prep: Preheat oven to 350°F (175°C) with rack in center. Line baking sheets with parchment. Ensure butter and egg are room temperature.
Make jam: In a small pot over medium heat, combine raspberries and sugar. Cook for 35-40 minutes, smashing berries halfway through. For seedless jam, press through fine mesh sieve. Stir constantly toward the end until thick and reduced to ⅓ cup. Remove from heat and chill completely.
Mix dry: In a medium bowl, whisk together flour, baking powder, baking soda, and salt for 30 seconds. Set aside.
Cream butter: In a large bowl, beat softened butter and sugar on medium-high for 2-3 minutes until light, fluffy, and pale.
Add wet ingredients: Add egg and vanilla. Mix until fully incorporated, scraping bowl as needed.
Combine dry ingredients: Reduce speed to low. Gradually add dry ingredients, mixing just until a soft dough forms and no flour remains. Do not overmix.
Layer jam: Push ¾ of dough to one side of bowl. Flatten remaining ¼ on bottom. Spoon ¼ of chilled jam onto it. Add another layer of dough, then jam. Repeat until all dough and jam are used, ending with jam.
Fold gently: Use a spatula to fold dough over itself just until jam streaks appear. Do not overmix, visible streaks should remain.
Portion: Scoop dough into 12 portions (2 tablespoons each). Roll each ball in sugar until coated.
Bake: Place on prepared baking sheets, 2 inches apart. Bake for 11-12 minutes, until edges are set and lightly golden.
Cool on sheet: Let cookies cool on baking sheet for 10 minutes.
Transfer and serve: Carefully transfer to a wire rack to cool completely, or enjoy warm.
