To make the Pomegranate Gelee

Pour the pomegranate juice into a measuring cup. Sprinkle the gelatin over the surface, and set aside for about 5 minutes to soften. Then pour into a small saucepan, add the sugar and heat over low heat just to dissolve the gelatin and sugar. Do not allow to boil. Remove from the heat and pour into an 8-inch round pan. The mixture should be about 1/8 inch deep. Cover and refrigerate until set, about 1 hour.

To make the pastry

In a food processor, combine the flour, sugar, cornmeal, lemon zest, lime zest, and salt and pulse 3 or 4 times to blend. In a small bowl, mix together the egg yolk and vanilla just to combine. Scatter the butter pieces over the flour mixture and continue to pulse just until the ingredients come together.

Transfer the dough to a work surface. Beginning at the far end, and using the heel of your hand, push a small amount of the dough (about the size of an extra-large egg) away from you, smearing it on the work surface. Repeat with the remaining dough in this manner, give it a couple more strokes to bring it together into a smooth, homogenous unit. (This kneading technique . . . is known as fraisage.) Flatten the dough into a disk. Wrap in plastic wrap and refrigerate until chilled and slightly firm, at least 1 hour or up to 3 days.

Before baking

Center a rack in the oven and preheat the oven to 375 degrees F. Have ready a 9 1/2 by 1-inch round fluted tart pan with a removable bottom.

Remove the dough from the refrigerator. If it is too firm to roll, let sit at room temperature until it is malleable enough to roll yet still cool to the touch, 15-30 minutes. Press the dough evenly into the bottom and up the sides of the tart pan. Or, roll out the dough on a lightly floured work surface into a 12-inch circle 1/8 to 3/16 inch thick. (Although this is a tart, the pastry is more like a pie pastry . . . ) Roll up the pastry around the rolling pin, and suspend the pin about 1 inch above the pan. Aligning the edge of the dough with the rim of the pan farthest from you, unroll it toward you. Then gently fit the dough into the pan, easing it into the crevices and up the sides. Trim away the excess dough by rolling the pin over the top of the pan. (Save any scraps for another use, if desired.)

Bake the tart shell until it is pale gold and the surface no longer looks wet, raw, or shiny, 15 to 20 minutes. Check after baking for about 5 minutes. If the pastry is puffed up, prick the center of the blistered area with a metal or wooden skewer or fork tines to release the steam. Don’t prick more than is needed. Transfer to a wire rack and let cook while you prepare the filling. Leave the oven on.

To make the Lemon Custard Filling

In a medium bowl, beat the eggs with a fork just to combine. Add the sugar, lemon juice, and lime juice and mix just until blended. To remove any unincorporated egg to create a smooth filling, pour the mixture through a fine-mesh sieve set over another bowl. Stir in the cream slowly just until blended.

Place the tart pan on a rimmed baking sheet to catch drips), and carefully pour the filling into the pastry shell. Place the tart on the baking sheet in the oven and bake until the filling appears set yet shiny on top, the center quivers a bit when the pan is gently shaken, and the edges of the crust are golden, 18 to 20 minutes. Transfer to a wire rack and let cool on the pan for about 20 minutes. Set the tart pan on a narrower elevated surface, such as a tin can, so the bottom of the pan is released as the metal rim slips down. Return the tart to the wire rack and let cool to room temperature.

To serve

At least 30 minutes before serving, remove the gelle from the refrigerator. With the tip of a paring knife, cut lines about 1/8 inch apart in both directions (the pattern will look like graph paper) to form the pomegranate jewels.

With a wide metal spatula (similar to what you would use to turn pancakes), lift the gelee over the lemon filling. Then scatter the pomegranate seeds over the top. Refrigerate the tart just long enough to chill the gelee pieces, about 30 minutes.

Cut the tart in to wedges with a sharp knife.