In a medium saucepan, whisk together the sugar, cornstarch, lemon zest, and a splash of the coconut milk until smooth.

Add the remaining coconut milk and whisk again until fully combined.

Place the pan over medium heat and cook, stirring constantly, until thickened — about 5 minutes. The custard should be thick enough that a trail made by your whisk takes 2–3 seconds to disappear.

Remove from heat and stir in the lemon juice.

Transfer to a medium bowl, press plastic wrap directly onto the surface to prevent a skin from forming, and refrigerate for at least 1 hour until fully chilled.

In a small saucepan, combine the raspberries and sugar.

Cook over medium heat, stirring regularly, until the raspberries break down and the sauce thickens slightly — about 3–5 minutes. When you drag a spatula through the mixture, it should take about 1 second for the gap to fill back in.

Remove from heat and chill until ready to use.

In small glasses or bowls, layer the chilled custard with fresh blueberries and raspberry coulis.

Sprinkle with toasted coconut flakes.

Serve immediately or keep refrigerated for up to 4 days.