Heat oven to 350℉/177℃.
Spray an 8-inch square pan with baking spray. Set aside.
In a medium bowl, whisk together flour, baking powder, baking soda, and salt. Set aside.
With an electric mixer, beat butter, cream cheese, peanut butter, and granulated sugar until no lumps of cream cheese remain and the mixture is light and fluffy.
Add eggs, one at a time, beating well after each.
Add flour mixture alternately with milk, beginning and ending with flour.
Stir in vanilla.
Spoon half of batter into prepared pan.
Top with strawberry jam.
Spoon other half of batter on top of jam.
Top with streusel.
Bake for 50 minutes, or until cake tests done.