Preheat oven to 350 degrees F. Lightly grease and flour three 8-inch round cake pans. In a medium bowl stir together flour, baking powder, and salt.
In a large bowl beat butter and peanut butter with a mixer on medium to high 30 seconds. Gradually add sugar, 1/4 cup at a time, beating on medium until combined. Scrape bowl; beat 2 minutes more. Add eggs, one at a time, beating after each. Beat in vanilla. Add flour mixture and milk alternately, beating on low after each addition just until combined. Spread batter into prepared pans.
Bake 30 to 35 minutes or until toothpick comes out clean. Cool cake layers in pans 15 minutes. Remove layers from pans; cool on wire racks.
Place one cake layer on a platter. Spread with 1/4 cup jam. Top with second layer, spread with 1/4 cup jam, and top with the third layer. Frost top and sides with Creamy Peanut Butter Frosting. Microwave remaining jam until smooth and thin enough to drizzle, stirring as needed. Drizzle melted jam over cake.
Creamy Peanut Butter Frosting
In a large mixing bowl beat cream cheese, peanut butter, butter, and vanilla with a mixer on medium until light and fluffy. Gradually beat in powdered sugar. Beat in enough milk (2 to 3 Tbsp.) to reach spreading consistency.