Heat oven to 200C/fan 180C/gas 6. Drain the fruit reserving the juice. Toss berries with 1 tbsp sugar, then spread in an even layer in a 24cm round ovenproof dish, greased with vegetable spread.
Sift the flour and cinnamon into a large bowl and stir in the remaining sugar. In a jug, beat the eggs and coconut milk together, then whisk into the flour mixture to make a smooth batter. Pour the batter slowly over the fruit then bake for 40-45 mins.
Heat the squash and reserved juice in a pan. Stir in the arrowroot until thickened. Dust the clafoutis with icing sugar and serve drizzled with the coulis.