Preheat your oven to 375°F (190°C). Line a muffin tin with paper liners to keep cleanup easy.
In a medium bowl, combine the flour, baking powder, salt, sugar, and lemon zest, whisking them together until evenly mixed.
In another bowl, whisk together the eggs, milk, vegetable oil, vanilla extract, and fresh lemon juice until well blended.
Gradually add the wet mixture to the dry ingredients, stirring gently until just combined. Avoid overmixing to keep the muffins light and tender.
In a separate small bowl, mix the softened cream cheese and powdered sugar until smooth and creamy. This will be your creamy swirl filling.
Fill each muffin liner halfway with batter, add a small spoonful of the cream cheese filling in the center, then top with more batter until about two-thirds full.
Bake for 20 to 25 minutes, or until a toothpick inserted in the center comes out clean. Let the muffins cool in the pan for a few minutes before transferring them to a wire rack to cool completely.
