How to Make It
Preheat oven to 350°F. Line a 9-by-13-inch baking pan with foil, leaving a 2-inch overhang on both long ends. Mist foil with cooking spray.
Pulse pecans and sugar in a food processor until finely ground. Pulse in flour, baking powder and salt. Pulse in 16 Tbsp. butter until mixture resembles coarse meal. Transfer half of mixture to a bowl, cover and chill. Pulse egg and yolk with mixture in processor until dough forms a ball. Press dough into a thin, even layer in baking pan. Bake until lightly browned around edges and set in center, 20 minutes. Let cool slightly.
Using your fingers, work remaining 2 Tbsp. butter into reserved crumble mixture. Spread jam evenly over crust. Spread crumble mixture over jam. Bake until top is golden, 30 to 35 minutes. Let cool on a rack for at least 1 hour. Lift bars from pan and place on a rack to cool completely. Peel off foil and cut into 24 bars.