Preheat your oven to 350°F (175°C). Grease a 9x5-inch loaf pan with butter or cooking spray, then line it with parchment paper, leaving some overhang on the sides. This makes it easy to lift the bread out of the pan after baking.

In a medium bowl, whisk together 2 cups of all-purpose flour, 1 tablespoon of baking powder, and 1/2 teaspoon of salt. Set this aside while you prepare the wet ingredients.

In a large bowl, whisk together 1/2 cup of natural peanut butter, 3/4 cup of granulated sugar, 2 large eggs, 1 cup of milk, and 1 teaspoon of vanilla extract. Whisk until the mixture is smooth and well combined.

Gradually add the dry ingredients to the wet ingredients, stirring gently with a spatula or wooden spoon until just combined. Be careful not to overmix—this keeps the bread tender and moist.

Pour half of the batter into the prepared loaf pan. Use a spoon to dollop 1/4 cup of your favorite jelly or jam over the batter. Use a knife to swirl the jelly into the batter, creating a marbled effect.

Pour the remaining batter into the pan, then add another 1/4 cup of jelly on top. Swirl gently with a knife to create more pockets of fruity sweetness.

Place the loaf pan in the preheated oven and bake for 50-60 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs. If the top starts to brown too quickly, cover it loosely with aluminum foil.

Remove the bread from the oven and let it cool in the pan for 10-15 minutes. Use the parchment paper overhang to lift the bread out of the pan and transfer it to a wire rack to cool completely. Slice and enjoy!