Spray 6 (4-inch) tart pans with removable bottoms with cooking spray or a 9-inch pie pan with cooking spray. Combine graham cracker crumbs and melted butter in a mixing bowl and mix until fully combined. Press the mixture firmly into the tart pans. Bake for 10 minutes or until golden brown. Let cool.
In the bowl of an electric mixer fitted with a paddle attachment, beat the cream cheese, sugar, and collagen until smooth. Add the lemon juice and zest and mix well.
In a clean bowl, whip the cream using the whisk attachment until stiff peaks form. Take a big scoop of the whipped cream and stir it into the cream cheese mixture to lighten it up and then gently fold in the rest of the cream cheese mixture. Spoon into cooled tart crusts. Cover lightly with plastic wrap and refrigerate for at least 4 hours. Can be made 1 day ahead.