Directions:

1. Place halved, pitted plums in a large bowl. Toss with 4 tablespoons sugar and a pinch of salt. Let sit at least an hour, stirring often, until plums have given off quite a bit of juice.

2. Place a heavy, ovenproof 10-inch skillet over medium-high heat. Melt butter and then add a pinch of salt, lemon zest and 12 tablespoons sugar. Cook, swirling pan or stirring often, until you have a medium-gold caramel, about 5 minutes. Don't let it get any darker, as it will continue to darken as it cools. Remove pan from heat. Cool for at least 20 minutes.

3. Drain plums and discard liquid. Place plums on top of caramel—overlapping and tightly packed, as the fruit will shrink as it cooks—cut-side down, in tight concentric circles.

4. Return pan to stove, over medium-low heat, and simmer plums in caramel without stirring for 20 minutes. Cool completely (for best results, refrigerate for at least 2 hours).

5. Bake the tart: Preheat oven to 375 degrees. Remove puff pastry from freezer and thaw until just malleable, about 10 minutes. Cut an 11-inch circle from pastry, prick a few holes in it with a fork, and place over plums, tucking edges in around fruit. Brush pastry with beaten egg and sprinkle with remaining 2 tablespoons sugar.

6. Bake in upper third of oven until pastry is deep golden brown and cooked through, 50-60 minutes. Remove and cool for 1 hour. Invert onto a large serving plate. Replace any plum pieces that have fallen out. Or, for a more rustic look and crisper crust, do not invert and serve right out of pan. Serve with vanilla crème fraîche.

Vanilla Crème Fraîche

Stir crème fraîche together with vanilla extract and sugar. Refrigerate until ready to use.