Line bottom and sides of an 8 or 9-inch square baking pan with aluminum foil or parchment, leaving an overhang on all sides to easily lift bars out of pan before cutting. Set aside.
Mix graham cracker crumbs and melted butter together in a medium bowl until combined.
Evenly press crust into prepared baking pan. Bake for 8 minutes. Remove from the oven and set aside.
Filling:
In a large bowl using a handheld or stand mixer fitted with a whisk attachment, beat cream cheese on high speed until completely smooth, about 1 minute.
On medium-high speed, beat in yogurt until completely combined.
Then beat in eggs and egg yolk until combined.
Beat in sugar, lemon juice, lemon zest, and vanilla extract until everything is combined and no lumps remain.
Pour filling onto crust. Bake for 25-30 minutes or until center bars no longer jiggles. (remove from oven and gently wiggle the pan to check)