Pulse the crackers in a food processor until very finely ground. Add the butter and sugar and pulse until thoroughly combined. Remove a rounded tablespoon of the crumb mixture and set aside.
Turn the mixture out into a 9-inch fluted tart pan with a removable bottom set on a cookie sheet and press evenly along the bottom and up the sides. Bake until light golden, about 15 minutes. Lightly press down on the crust if it has puffed up on the bottom.
Spoon the preserves into the tart shell and gently smooth to spread evenly. Sprinkle the reserved crumbs on top. Bake until the jam is a shade darker and the edges are bubbling slightly, 20 to 25 minutes. Cool completely on a rack.
Serve at room temperature with whipped cream, if using.