Preheat oven 350 degrees. Prepare a tart or pie pan by spraying liberally with non-stick spray. Place it on a large baking sheet {to ensure no drips and to make it easier to move in and out of the oven}; set aside.
Make crust: In the bowl of a food processor, combine graham cracker crumbs and coconut flakes. Pulse until the coconut is processed into fine bits. Pour into a small bowl and add melted butter. Toss to combine until the crumbs resemble wet sand. {It should be able to somewhat stick together when pressed.} Press the mixture into the prepared tart or pie pan, using a measuring cup to evenly flatten the bottom and up the sides of the pan.
Bake crust for about 8-10 minutes or until it begins turning golden brown. Remove from oven and let cool.
Clean out the food processor. Add sweetened condensed milk, egg yolks (not whites), vanilla extract and orange zest; blend until the mixture is a pale yellow color.
While the processor is still running, pour in the orange juice and blend until fully combined.
Meanwhile, beat the egg whites until stiff peaks form. Set aside.
Slowly pour little bits of the orange/egg yolk mixture into the beaten egg whites, folding gently. Make sure not to deflate the egg whites but ensure that everything is becoming uniform without too many lumps.
Pour the mixture into the cooled crust and bake for another 18-20 minutes or until the top is lightly golden and the custard is just set -- it should have a tiny bit of "jiggle" left. Remove from oven and cool completely.
Make Whipped Cream: Beat cream, sugar and vanilla extract until soft peaks form. Scoop into a piping bag with a decorative tip {if desired} and pipe around the edge of the cooled tart. Decorate with thin orange slices if desired.
Refrigerate for at least 2 hours before serving.