8 tbsp. unsalted butter, at room temperature
¼ cup creamy peanut butter
½ cup sugar
Pinch of coarse salt
1 tsp. vanilla extract
1¼ cups all-purpose flour
2/3 cup jam (strawberry, grape, or whatever flavor you prefer)
Lightly spray a 9-inch springform pan with cooking spray, or grease lightly with butter. (A 9-inch round cake pan would work too.) Beat together the butter and peanut butter with an electric mixer on medium-high speed until smooth, 1-2 minutes. Mix in the sugar and salt and beat until fluffy, about 2 minutes. Blend in the vanilla. Beat in the flour on low speed just until incorporated. Reserve 1/3 cup of the dough, flatten into a disk and wrap tightly in plastic wrap. Freeze until very firm, about 1 hour.
Meanwhile, press the remaining dough into the prepared pan, leaving ½-inch border to create a lip around the edge. Spread the jam in an even layer over the dough, reaching to the raised edges. Refrigerate until the dough disk is firm.
Preheat the oven to 350˚ F. Break the frozen dough disk into small crumbles and sprinkle evenly over the layer of jam. Bake until the edges of the dough are golden brown, about 50 minutes. Transfer to a wire rack and allow to cool completely before cutting. Slice into wedges and serve.