Preheat the oven to 350 degrees F. Line a muffin tin with 9 liners and fill up half of the other empty spaces with water. This ensures even baking.
In a food processor, pulse the graham crackers to crumbs. Stir in the sugar and melted butter. Press an even amount of graham cracker crust into the bottom of each muffin liner.
Press down the crust with a milk cap or the backside of a tablespoon measuring spoon and set aside.
In a medium sized bowl, combine the softened cream cheese and white sugar. Beat until smooth and creamy. Add in the vanilla extract, egg, and lemon zest. Beat until combined.
Spoon the cheesecake filling evenly between the 9 cups and bake for 20-22 minutes. The centers will still jiggle a little bit, but the edges should be a very light brown.
Remove from the oven and let cool at room temperature for 30 minutes and then transfer to the fridge and let cool for at least 2 hours.
The cheesecakes may have risen in the oven and will deflate quite a bit while cooling.
Once the cheesecakes have been cooled for 2 hours in the fridge, place 4 and 1/2 tablespoons of blueberry jam in a small bowl and microwave for 20-25 seconds. Spoon 1/2 tablespoon of jam on top of each cheesecake and spread to cover the top.
Immediately top with fresh blueberries.
Places the last 1 and 1/2 tablespoon in the same small bowl and microwave for 10-15 seconds. Using a pastry brush, brush the tops of all of the fresh blueberries with the jam. Sprinkle powdered sugar on top if desired.