Preheat the oven to 375°F., To make the crust: Stir together the crumbs, sugar, salt, cinnamon, and melted butter., Press into the bottom and about 1/2" inch up the sides of an 8" x 8" square pan., Freeze for 15 minutes if using a metal pan (not necessary if using ceramic or glass). Note: this is to prevent the edges of the crust from slumping. If you're not worried about slumping (and in our testing, it only happened some of the time), you can skip this step., Bake the crust for 8 to 10 minutes, until set; the color won't change much., Remove the crust from the oven and cool for a few minutes while you lower the oven temperature to 325°F., To make the batter: Mix the cream cheese and sugar together until smooth., Add the cream, eggs, vanilla, lemon zest, and lemon juice; mix until combined, scraping the sides and bottom of the bowl as you mix., Spoon the batter into the crust., Bake the bars for 30 to 40 minutes, until the filling is set but still soft in the center. An instant-read thermometer, inserted into the filling about 1" in from the edge, will read about 180°F., Remove the bars from the oven, and cool at room temperature for 30 minutes. Refrigerate until ready to serve., Just before serving, top with fresh berries, fruit pie filling, or whipped cream.