Preheat oven to 350°F. Line a 15½" X 10½" X 1" jelly roll pan with nonstick foil.
Pulse flour and hazelnuts in a food processor until nuts are finely ground.
In a large bowl, beat butter and sugar with an electric mixer on medium speed, until creamy. Add yolks, cinnamon, lemon zest, vanilla, and salt; beat until well blended.
Switch mixer to low speed, add flour mixture and beat until combined. Reserve 1 1/3 cups of the dough; divide in half and roll each half into a 12-inch log. Wrap logs in plastic wrap and refrigerate.
Pat remaining dough evenly over bottom of pan. Bake in preheated oven until edges are golden brown, about 20 minutes. Let cool on a wire rack.
Drop jam by teaspoonfuls over crust up to ¼ inch from edges.
Cut refrigerated dough into ¼-inch-thick slices. Arrange over jam, leaving space between slices. Bake 40 to 45 minutes, or until top is slightly golden brown and filling starts to bubble in spots. Cool completely on wire rack.
Remove from pan to a cutting board. Cut into 40 bars. Dust lightly with confectioners' sugar before serving.
141 calories (1g protein, 23g carbohydrate, 5g fat) per serving