Make the pastry by adding the flour, butter and salt to a food processor. Blend until the mixture resembles breadcrumbs. Add in the sugar, cornstarch and water. Blitz until the dough comes together. Then turn out onto a work surface and form into a ball. Wrap in cling film and place in the fridge for 30 minutes.
Peel and slice the pineapple into wedges, 1/2 cm thick. Pre heat the oven to 200C/ 180C fan.
Add the sugar and water to a large saucepan and heat over a moderate-high heat. Cook for approximately 5 minutes or until the sugar crystallises then turns a deep golden-brown. Keep a close eye on the caramel as it can easily burn!
Remove from the heat and stir in the butter and salt. Return to the heat and simmer for a minute to thicken.
Next add the sliced pineapple and coat in the caramel sauce. Place the lid on, after 10 minutes remove the lid and cook for a further 5 minutes to allow the caramel to reduce and thicken.
Use tongs to arrange the pineapple in overlapping concentric rings in a 21cm deep walled cake tin. Ladle over 3 tbsp of the caramel sauce leaving behind some sauce to serve.
Roll the pastry on a well floured surface. Cut out a circle just slightly larger than the cake tin and poke holes all over. Carefully place the pastry over the pineapple and caramel mix.
Tuck the edges of the pastry down the sides of tin. Place in the oven for 35 minutes at 200C / 180C fan.
Remove from the oven and allow to cool in the tin for 10 minutes. Then use a knife to loosen the tart from the tin. Place a plate over the tin and carefully invert. Serve with dairy free ice cream, crushed almonds and the remaining warm caramel sauce.