Preparation Put oven rack in middle position and preheat oven to 350°F. Line a 9-inch square baking pan with foil. Beat together butter, peanut butter, and brown sugar in a large bowl with an electric mixer at medium speed until fluffy, about 2 minutes. Add egg and beat until combined. Mix in flour and salt at low speed until a dough forms. Reserve 1 cup dough for topping. Press remaining dough evenly in bottom of baking pan. Spread jelly in an even layer on top of dough, then coarsely crumble reserved dough over jelly layer. Bake until top is golden, 30 to 35 minutes. Cool completely in pan on a rack, about 45 minutes, then cut into bars.
Preparation Put oven rack in middle position and preheat oven to 350°F. Line a 9-inch square baking pan with foil. Beat together butter, peanut butter, and brown sugar in a large bowl with an electric mixer at medium speed until fluffy, about 2 minutes. Add egg and beat until combined. Mix in flour and salt at low speed until a dough forms. Reserve 1 cup dough for topping. Press remaining dough evenly in bottom of baking pan. Spread jelly in an even layer on top of dough, then coarsely crumble reserved dough over jelly layer. Bake until top is golden, 30 to 35 minutes. Cool completely in pan on a rack, about 45 minutes, then cut into bars.