step one, Mix lemon zest with sugar

1. Start by combining the lemon zest with the granulated sugar in a large mixing bowl. Rub the zest into the sugar with your fingers until fragrant. This step enhances the flavor of your blueberry muffins with a burst of fresh citrus.

step two, Add the dry ingredients

1. Add the all-purpose flour and baking powder to the sugar mixture. Whisk everything together to evenly distribute the dry ingredients.

step three, wet ingredients

1. Crack the eggs directly into the bowl with the dry ingredients. Add the melted butter and milk. Gently fold the mixture together until just combined. Be careful not to overmix to keep your muffins light and fluffy.

step four, add the frozen blueberries

1. Carefully fold in the frozen blueberries. A few gentle stirs are all you need to incorporate them into the batter while keeping the berries intact.

step five, preheat the oven

1. Preheat your oven to 410°F (210°C).

step six, fill the muffin tin

1. Line a muffin tin with paper liners. Divide the batter evenly among the liners, filling each about ¾ full.

step seven, add blueberry jam swirls

1. Place a big tablespoon of blueberry jam on top of each muffin. Use a toothpick or skewer to swirl the jam into the batter, creating a beautiful pattern.

step eight, bake the muffins

1. Bake the muffins in the preheated oven at 410°F (210°C) for 13 minutes.Lower the temperature to 340°F (170°C) and continue baking for another 8 minutes. Check if the muffins are done by inserting a toothpick into the center, it should come out clean or with a few moist crumbs.

step nine, cool and enjoy

1. Let the muffins cool in the tin for 5 minutes before transferring them to a wire rack. Enjoy your homemade blueberry jam muffins warm or at room temperature!