Line the bottom of a 9-inch springform pan with parchment paper. Lightly grease the sides. This ensures clean release later.
Stir graham cracker crumbs, ⅓ cup sugar, and melted butter until the mixture looks like wet sand. Press firmly into the bottom of the pan using the bottom of a measuring cup. Chill while you prepare the filling so the crust firms up.
In a large bowl, beat softened cream cheese with an electric mixer on medium speed until completely smooth, about 1–2 minutes. Scrape the bowl once. Add powdered sugar, vanilla, and lemon juice. Beat again until creamy and no lumps remain.
In a separate cold bowl, whip the heavy cream to stiff peaks. The cream should hold its shape when the beaters are lifted. Gently fold the whipped cream into the cream-cheese mixture in two additions until no white streaks remain. The filling should look light and fluffy.
Spread the filling evenly over the chilled crust. Smooth the top with an offset spatula. Cover and refrigerate at least 4 hours, preferably overnight, until the center feels firm to a gentle touch.
While the cheesecake chills, combine sliced strawberries and ¼ cup sugar in a small saucepan over medium heat. Cook 3–4 minutes until the berries release juice. Stir in the cornstarch slurry and lemon juice. Simmer 1–2 minutes more until the sauce thickens and turns glossy. Cool completely.
Spoon the cooled strawberry topping over the set cheesecake. Release the springform ring, slice with a sharp knife wiped clean between cuts, and serve chilled.