Step 1

Place a rack in middle of oven and preheat to 425°. Cook honey, sugar, salt, and 2 Tbsp. water in a small saucepan over medium-high heat, stirring occasionally, until caramel turns dark amber in color (because of the honey, it can be hard to tell when the color changes; it should look like maple syrup). Remove caramel from heat and add butter and vinegar (be careful; mixture will bubble up). Stir with a wooden spoon or heatproof rubber spatula to incorporate.

Step 2

Pour caramel into a 9"- or 10"-diameter cake, tart, or springform pan or skillet and swirl to evenly coat the bottom.

Step 3

Arrange apricots, cut side down, in pan, letting them overlap slightly if needed. (Depending on the pan you use, you may not need all of them.)

Step 4

Unfold pastry and gently roll out on a lightly floured surface just to soften the creases and corners. Prick pastry all over with a fork. Drape over pan, then, using kitchen shears, trim to make a circle that’s slightly larger than the circumference of the pan (remember, the dough will shrink as it bakes) and tuck into pan.

Step 5

Bake tart until pastry is puffed and just golden, 15–20 minutes. Reduce oven temperature to 375° and continue to bake until pastry is deep golden brown and fruit juices are bubbling, 15–20 minutes longer. Transfer tart to a wire rack and let cool 10 minutes.

Step 6

Invert a large plate over the top of the pan. Using a dish towel or oven mitts, flip tart over onto plate. Carefully remove pan. Top tart with pistachios.

Step 7

Serve tart with whipped cream or ice cream if desired.

Step 8

Do Ahead: Tart can be baked 4 hours ahead. Leave in pan at room temperature. If caramel has set too firmly to release from pan, heat in a 375° oven 5 minutes to warm and loosen before turning out.