Prep the pan. Heat the oven to 375°F (190°C). Line a 12-cup muffin tin with paper liners or lightly grease it.
Whisk dry ingredients. In a medium bowl, whisk 2 cups all-purpose flour, 2 teaspoons baking powder, 1/2 teaspoon baking soda, and 1/2 teaspoon salt. Set aside.
Mix the wet ingredients. In a large bowl, whisk 1/2 cup creamy peanut butter, 1/3 cup neutral oil, 1/2 cup brown sugar, and 1/3 cup granulated sugar until smooth.
Whisk in 2 large eggs, 1 cup plain Greek yogurt (or buttermilk), and 2 teaspoons vanilla until combined.
Combine gently. Add the dry ingredients to the wet. Stir with a spatula just until no dry streaks remain. The batter should be thick but scoopable.
Do not overmix.
Fill the cups. Spoon about 1 heaping tablespoon of batter into each muffin cup. Add 1 to 1 1/2 teaspoons of jam on top. Cover with another tablespoon of batter, sealing the jam inside.
Optional swirl and topping. If you like, add a tiny dot of jam on top and swirl with a toothpick.
Sprinkle with chopped peanuts or coarse sugar for crunch.
Bake. Bake 16–20 minutes, until the tops are set, lightly golden, and a toothpick inserted into the muffin (avoiding the jam pocket) comes out clean.
Cool. Let the muffins rest in the pan for 5 minutes, then transfer to a rack to cool. The crumb sets as they cool, so try to wait 10–15 minutes before eating.