Prep the pan and oven. Heat the oven to 325°F (163°C). Line the bottom of a 9-inch springform pan with parchment paper. Lightly spray the sides with cooking spray.
Make the crust. In a bowl, mix crushed graham crackers, sugar, melted light butter, and a pinch of salt until it looks like damp sand.
Press firmly into the bottom of the pan in an even layer. Bake for 8–10 minutes, then set aside to cool.
Beat the cream cheese. In a large bowl, beat the reduced-fat cream cheese on medium speed for 1–2 minutes until smooth and fluffy. Scrape down the sides halfway to avoid lumps.
Add yogurt and sweetener. Mix in Greek yogurt and sugar (or sweetener) until smooth.
Don’t overbeat; just blend until combined.
Thicken and flavor. Add cornstarch, vanilla, lemon zest, lemon juice, and a pinch of salt. Beat on low until incorporated.
Add the eggs. Beat in the eggs and egg white one at a time on low speed. Stop as soon as the mixture looks uniform.
Overmixing adds air, which can cause cracks.
Pour and smooth. Pour the filling over the cooled crust and smooth the top with a spatula. Tap the pan gently on the counter to release air bubbles.
Bake gently. Place the springform pan on a baking sheet. Bake at 325°F (163°C) for 40–50 minutes.
The edges should be set, and the center should still wobble slightly like Jell-O.
Cool gradually. Turn off the oven, crack the door, and let the cheesecake rest inside for 45–60 minutes. This slow cool helps prevent cracking.
Chill overnight. Move the cheesecake to a rack to cool to room temp, then cover and chill at least 6 hours or overnight. Chilling firms the texture and deepens the lemon flavor.
Make the blueberry topping. In a small saucepan, add blueberries, water, lemon juice, and sugar or sweetener.
Simmer over medium heat for 3–4 minutes, stirring occasionally until the berries start to burst.
Thicken and cool. Stir in the cornstarch slurry and cook 30–60 seconds, until slightly glossy and thickened. Remove from heat and let it cool completely.
Top and serve. Release the chilled cheesecake from the pan. Spoon the cooled blueberry topping over the surface.
Garnish with lemon zest or fresh berries. Slice with a warm, thin knife for clean edges.