Position rack in lower third of oven; preheat to 350 degrees F. Grease a 9-inch springform pan.
For crust, mix together crumbs, sugar, and cinnamon; stir in butter. Press evenly and firmly over bottom and half way up sides of pan. Bake 10 to 12 minutes; cool on wire rack. Grease sides of pan again above crust level to prevent filling from sticking to pan.
Preheat oven to 325 degrees F. In mixing bowl, with an electric mixer, beat cream cheese 30 seconds. Scrape bowl and beaters. Add sugar and vanilla. Beat until smooth and creamy, 1-1/2 minutes. Beat in 1 egg just until combined. Scrape bowl and beaters. Beat in remaining egg. Pour into crust.
Stir together caramel sauce, peanut butter, and a pinch of salt. (If stiff, heat a few seconds in microwave to soften.) Spoon pools of caramel mixture over plain batter, making sure to leave some plain batter showing. Jiggle pan gently to settle caramel mixture level with plain batter. Marble the batters with a small spoon by gently whirling in small, loopy circles until intermingled but not blended. Place pan on a baking sheet.
Bake 40 to 45 minutes, or until edges are puffed but center looks moist and jiggles when pan is nudged. Remove from oven. If batter is touching sides of pan, above crust, slide a thin knife carefully around edges to detach cake; do not remove sides. Place pan on rack. Cover pan and rack with large inverted bowl or pot so cake cools slowly. Once cool, cover and refrigerate 5 to 24 hours. Remove sides of pan before serving. Makes 10 to 12 servings.