In a food processor, pulse almonds and sugar until very finely ground. Add butter and process until smooth, about 1 minute. Scrape dough down from the sides of the processor. Add vanilla and almond extracts and pulse a few times to combine. Add flour and salt and pulse until a soft dough forms. Turn dough out onto a large piece of waxed paper and roll into a log about 15 inches long and 1-½ inches wide. Wrap and refrigerate 30 minutes. Heat oven to 325º. Slice dough into ½-inch-thick pieces and flatten until about ¼ inch thick. Spoon ¼ teaspoon preserves into center of each piece. Fold in sides and gently roll into a ball. Place on a baking sheet lined with parchment paper or Silpat (a silicone baking sheet), and press gently to slightly flatten. Bake about 8 minutes; then rotate baking sheets. Bake another 8 to 10 minutes. Cool cookies briefly on a rack; then gently toss in confectioners’ sugar until evenly coated. Return to rack and let cool to room temperature. Then toss again in confectioners’ sugar.