1. Preheat oven to 350°F. Mist a 9-inch pie plate with cooking spray. Make crust: Spread pecans on a baking sheet; toast until nuts are golden and fragrant, about 8 minutes, shaking pan twice. Transfer to a bowl to cool; chop finely.
2. Mix pecans, graham cracker crumbs, sugar and butter until evenly moistened. Press into pie plate. Bake until edges are golden brown, about 10 minutes. Let cool on a wire rack.
3. Make filling: In a small bowl, sprinkle gelatin over 1/4 cup cool water; let stand for 5 minutes to soften. Using an electric mixer on medium-high speed, beat cream cheese, sugar, pumpkin pie spice and salt until smooth. Mix in pumpkin puree.
4. Place bowl of gelatin in a pan of simmering water and warm, stirring, until melted, about 2 minutes. When gelatin is clear and smooth, remove bowl and stir in 1/2 cup pumpkin filling. Fold gelatin mixture into remaining pumpkin filling. In a smaller bowl, whip cream until stiff peaks form, then fold into pumpkin filling. Spoon filling into pie crust and smooth top. Spoon apple butter around top of filling; press lightly into filling with spoon. Drag a small knife through apple butter in a swirl pattern to create a marble effect, taking care not to hit crust. Chill for at least 3 hours or overnight.