Using a hand mixer, cream together the softened butter and the sugar in a large bowl. You want to combine these two ingredients a bit longer than just until they are combined. It needs to become light and fluffy!

Add each egg, one at a time, and continue blending until smooth.

Add the vanilla extract, lemon juice, and buttermilk. Blend until just combined. Don't overmix at this step, particularly now that the egg has been added!

In a separate medium bowl, whisk together the flour, salt, and baking powder. This is to ensure that the baking powder is evenly distributed throughout the dry ingredients.

Fold the flour mixture into the wet ingredients, until fully combined and there are no more dry ingredient streaks.

Fold the blueberries into the muffin batter.

Using a hand mixer, cream together the softened cream cheese, sugar, vanilla, and cornstarch to make the cheesecake filling.

In muffin tins prepared with cupcake liners, use an ice cream scoop to fill each liner with 1/4 cup of batter.

Use a spoon to flatten the thick batter somewhat, then add a teaspoon of the cream cheese mixture to the center of each.

Top the creamy filling with more muffin batter, until each liner is 3/4 of the way filled.

Sprinkle sanding sugar on top of each muffin.

Bake the muffins for 24-30 minutes, or until an inserted toothpick comes out clean. Let cool slightly, then enjoy!