Preheat the oven to 200 °C (180 °C fan). Preheat a baking tray too.
Melt 30 g butter in a wide pan. Add wedges in a single layer; cook 2–3 min cut-side down until just glossy with the faintest colour, flip 30–60 sec. (Reduce any juices to a light syrup and keep.) Cook sugar and water to deep amber; off heat whisk in 60 g butter, salt, and vanilla. Put back on the heat and thicken for 2–3 min.
Place the caramel in a 24 cm metal tin (do not use the ones with detachable bottoms)
Pack apples very snugly, rounded sides down, points toward centre. Spoon over any reduced syrup
Cut a pastry circle 2–3 cm larger than the pan. Lay it over the fruit, tuck the edges down the inside of the pan, and cut 3–4 small vents
Place the tin on the hot baking tray and bake for 25–30 min until the pastry is puffed and deep golden and the caramel is bubbling up the sides.
Cool 5–10 min (this helps the caramel set slightly). Run a knife around the edge, place a plate over the pan, and invert carefully
