Preheat the oven to 350° Fahrenheit. Lightly grease a 9x13 inch pan, then line with parchment paper and grease again with butter or cooking spray.
In a large bowl, using an electric mixer, beat together the peanut butter, butter, brown sugar, and sugar until fluffy and slightly lighter in color. Add in the eggs, yogurt, and vanilla and continue to beat until fully combined.
In a separate, medium bowl, whisk together the flour, peanut butter powder, almond meal, starch, baking powder, and salt until combined. Pour these dry ingredients into the large bowl and stir everything together using a wooden spoon or spatula.
Pour batter into prepared pan and spread evenly to reach each corner. Then, using a spoon, put blobs or lines of jam on top of the batter and use a toothpick to create swirls or patterns that you like. Once you're happy with it, pop it in the oven for 35-45 minutes or until edges are just browned and center does not jiggle (the jam will still move but it will settle once it cools).
Let cool completely before slicing and serving! Best with a cold glass of milk.