Preheat the oven to 200C (fan oven 160), gas mark 6. Roll the pastry thinly on a lightly floured surface, then use to line a 34x11.5cm (13½ x 4½inch) loose-based tranche tin. Prick the base with a fork and pop in the freezer for 30 minutes.
Put the coconut on a baking sheet and toast in the hot oven for 1-2minutes until golden brown. It will burn very quickly so don’t leave it! Leave to cool.
Line the pastry case with foil, pressing it gently into the curves of the tin and folding it down over the outside edge. Fill with baking blind beans and bake on a baking sheet for 15 minutes. Remove the foil and beans and bake for a further 5-10 minutes or until the pastry is pale golden.
Meanwhile, measure the golden syrup and marmalade into a small saucepan. Warm over a gentle heat until melted and blended together. Stir in the breadcrumbs with 2 tablespoon of the coconut, the lemon zest, juice and the egg. Pour into the pastry case and scatter the blueberries on top. Sprinkle with the remaining coconut and bake for 30 minutes until just firm and golden brown.
Serve warm with chilled crème fraiche for pudding or cut into fingers for tea.
Prepare ahead.
The tart can be made up to 2 days ahead and kept in an airtight container, or freeze for up to 1 week.
The same pastry and mixture can be used with a shallow, 20cm (8inch) loose-based flan tin.
