Step 1

Heat oven to 400ºF. On lightly floured piece of parchment paper, roll puff pastry to 1/8-inch thick. Cut out a 12-inch round and refrigerate until ready to use.

Step 2

Peel, halve, and core pears, then cut each half in half. Rub pears with cut side of 1/2 lemon.

Step 3

Juice remaining half lemon. Heat medium cast-iron (about 10 inches) on medium. Add maple syrup, butter, salt, and lemon juice and cook, swirling pan occasionally, until mixture begins to thicken, deepen in color and smell like caramel, 5 to 8 min.; remove from heat. Being careful not to touch maple mixture, arrange pears, cut sides down, in pan. Return pan to low heat and cook pears 4 minutes. Remove from heat and lay puff pastry circle on top, carefully tucking overhang down inside of pan. Cut 3 small slits in pastry and bake in upper third of oven 10 minutes. Reduce temp to 375°F and bake until pastry is deep golden brown and maple mixture has reduced, 15 to 20 minutes.

Step 4

Let stand 5 minutes, then run knife along edge to loosen. Place plate on top and flip, inverting tart. Sprinkle with sliced almonds and serve warm or at room temperature.