Prepare the crust: Preheat oven to 350°F (175°C). In a mixing bowl, combine graham cracker crumbs, sugar, shredded coconut (if using), and melted butter. Mix until the crumbs are evenly coated.
Press into tart pan: Firmly press the mixture into the bottom and sides of a 9-inch tart pan. Bake for 8–10 minutes until lightly golden. Let it cool slightly.
Make the filling: In another bowl, whisk together coconut milk, sweetened condensed milk, lime juice, lime zest, and egg yolks until smooth.
Pour and bake: Pour the filling into the slightly cooled crust. Bake for 18–20 minutes, just until the center is set but still slightly wobbly.
Cool and chill: Allow the tart to cool at room temperature, then refrigerate for at least 4 hours or overnight.
Garnish and serve: Before serving, top with whipped cream, extra lime zest, or toasted coconut flakes if desired.