Jam and coconut tarts

Pastry

• 125 g unsalted butter, softened and cut into pieces, plus extra to grease
• 250 g plain flour, plus extra to dust
• 25 g white sugar
• 2 tsp baking powder
• 1 pinch sea salt
• 3 eggs, separated
• 20 g water
• 250 g smooth apricot jam

Topping

• 1 pinch cream of tartar
• 200 g caster sugar
• 150 g desiccated coconut