1) Preheat the oven to 325°F. Place eight 2 1/2" heart molds on a baking sheet. Or get out a standard muffin pan.
2) To make the crust: Combine the crumbs and sugar.
3) Add the melted butter and stir until evenly mixed.
4) Press the crumbs firmly into the bottoms of the heart molds, or 8 cups of the standard muffin pan.
5) To make the batter: Using an electric mixer, mix the room-temperature cream cheese, sugar, and flour at low speed until smooth. Scrape the bottom and sides of the bowl at least twice during this process to be sure no cheese is sticking.
6) Mix in the lemon zest, vanilla, and salt. Add the egg, mixing until incorporated. Stir in the sour cream.
7) Divide the filling among the heart pans or muffin cups, filling each about 3/4 full. Gently tap the pan on the counter to level the batter.
8) Bake the cakes for 16 to 20 minutes, until set around the edges with a still somewhat jiggly middle.
9) Remove from the oven, and cool for 30 minutes or so before refrigerating. Cover and refrigerate for several hours before unmolding cheesecakes.
10) Just before serving, garnish with fresh berries or fruit pie filling and whipped cream, if desired.