Step 1

Position a rack in the center of the oven and preheat to 350ºF. Coat an 8 × 8-inch baking pan with cooking spray or brush with butter. Line the pan with a strip of parchment paper that hangs over two of the edges.

Step 2

In a large bowl, whisk the sugar and eggs until pale and foamy, about 1 minute. Add the sour cream, peanut butter, melted butter, vanilla, and salt and whisk until smooth and emulsified.

Step 3

Whisk in the baking powder and baking soda. Fold in the flour with a spatula and mix until well combined.

Step 4

Pour the batter into the prepared pan, smooth the top, then dot the top with the jam. Use a skewer or thin knife to swirl the jam through the batter. If desired, scatter the raspberries over the top.

Step 5

Bake the cake until puffed and golden and a tester inserted into the center comes out clean, 40 to 50 minutes. This cake can be tricky to test for doneness, so try to choose a spot without jam to test.

Step 6

Let the cake cool in the pan on a rack for about 15 minutes, then use the parchment paper to lift the cake out and onto the rack to cool completely. Store loosely covered at room temperature for up to 3 days.