Line the bottom of a 9-inch springform pan with parchment; lightly grease the sides.
Stir graham crumbs, brown sugar, and melted butter until evenly moistened.
Press crumbs firmly into the pan bottom and 1 inch up the sides. Freeze 10 minutes to set.
Beat softened cream cheese until smooth. Add powdered sugar, vanilla, lemon juice, and salt; beat until creamy.
Whip cold heavy cream to medium peaks. Gently fold into the cream cheese mixture until no streaks remain.
Spread filling over the crust. Smooth the top, cover, and chill at least 6 hours or overnight.
Combine butter, dark brown sugar, corn syrup, heavy cream, cinnamon, and salt in a saucepan. Simmer 2–3 minutes, stirring.
Remove from heat. Stir in pecans and vanilla. Cool to room temperature until thickened but still pourable.
Spoon pecan topping over the chilled cheesecake. Chill 30 minutes to set before slicing.