Preheat oven to 428 degrees F.

Peel, core and halve the apples.

Put sugar in ovenproof frying pan along with 50ml of water

Stir consistently over low heat. After sugar has melted, turn up the heat and allow to bubble.

Once sugar turns a golden brown remove from the heat immediately. Stir in butter and sprinkle the caramel with sea salt.

Arrange apples halves over mixture with the cut-side facing up. Place pan back over low heat for about 5 minutes.

Remove from heat and allow apples to cool completely

Roll pastry out on floured surface. Place pastry over apples and trim excess edges.

Pinch and tuck edges of pastry down inside the edge of pan and around the apples.

Bake for @30 minutes until golden brown.

Remove from oven and allow to stand for @5 minutes. Carefully drain excess juice from pan and set aside.

Invert the tart onto a serving plate.

Reheat drained juice until bubbly, syrupy and thickened. Pour thick mixture back over the inverted tatin (optional).