Line an 8-inch square pan with parchment paper.
Mix graham cracker crumbs, melted butter, and sugar. Press into the pan and chill for 20 to 30 minutes.
Beat heavy cream to stiff peaks and refrigerate.
Beat cream cheese until smooth. Add powdered sugar, vanilla, and lemon juice, and beat until creamy.
Fold whipped cream into the cream cheese mixture. Spread over the chilled crust. Refrigerate at least 6 hours.
Cook strawberries, sugar, and lemon juice in a small saucepan for 3 to 5 minutes. Stir in cornstarch mixed with water and cook until slightly thickened. Cool completely.
Spoon topping over the cheesecake layer and chill 30 to 60 minutes more.
Lift from the pan, slice, and serve.