For the filling:
1. Pulse together flour, cornmeal, sugar, and salt in a food processor. Add butter and rosemary and pulse until mixture resembles coarse meal with some small (roughly pea-size) butter lumps. Drizzle evenly with 4 tablespoons ice water and pulse until just incorporated. Gently squeeze a small handful. If it doesn't hold together, add more water, 1/2 tablespoon at a time, pulsing after each addition and continuing to test.
2. Press dough evenly onto bottom and up sides of tart pan with floured fingers. Smooth dough with a small offset metal spatula or back of a spoon (floured if necessary), then roll a rolling pin over top of pan to trim dough flush with rim. Chill crust until firm, about 30 minutes.
3. Preheat oven to 400º. Bake crust in middle of oven until center and edges are golden, 25 to 30 minutes (don't worry if bottom of crust cracks), then cool in pan on a rack.
Prepare filling and assemble tart
4. Whisk together sour cream, mascarpone, sugar, zest, and salt in a bowl. Heat jelly and honey in a small saucepan over moderately low heat, whisking, until jelly is melted, about 4 minutes, then cool glaze slightly. Remove side of tart pan and spread mascarpone cream in shell. Cut figs lengthwise into 1/4-inch-thick slices and arrange decoratively over cream. Brush figs with honey glaze.
Note: Crust can be made 1 day ahead and kept, covered, at room temperature. Mascarpone mixture can be made 1 day ahead and chilled, covered. Tart can be assembled 1 hour ahead and kept, loosely covered, at room temperature.
Sandor Katz lives to ferment; it’s his life’s work. The author of The Art of Fermentation shares how to make kombucha at home.