Preparation Spray bottom of 9-inch-diameter springform pan with nonstick spray. Beat butter and peanut butter in large bowl until smooth, about 2 minutes. Add sugar and salt and beat until fluffy, about 2 minutes. Beat in vanilla. Add flour; beat on low speed just until blended. Transfer 1/3 cup dough to work surface. Shape into 1/2-inch-thick disk, place on plate, and freeze until hard, about 1 hour. Press remaining dough evenly over bottom of prepared pan. Spread jam over dough in pan, leaving 1/3-inch plain border. Refrigerate while dough disk freezes. Preheat oven to 350°F. Using large holes of box grater, grate frozen dough evenly over jam. Bake shortbread until dough edge is deep golden and grated dough on top looks dry and baked through, about 50 minutes. Cool shortbread completely in pan. Release pan sides. Cut shortbread into wedges. DO AHEAD: Can be made 1 day ahead. Store airtight at room temperature.