Preheat oven to 350ºF. Prepare an 8-inch or 9-inch baking pan with nonstick cooking spray.
In a medium bowl, whisk together coconut oil, vanilla extract, lime zest, egg yolks and eggs until well blended. Set aside. In another, smaller bowl, whisk together flour, salt, baking soda, and sugar. Add dry ingredients to wet ingredients and lightly whisk until just combined. In a clean medium bowl, beat the remaining egg whites with an electric mixer until soft peaks form. Gently fold beaten egg whites into the batter and then pour the mixture into prepared pan.
Bake in a 350°F oven for 20 minutes or until a toothpick inserted into the center comes out clean. Allow cake to cool for five minutes and then, using a wooden skewer, chopstick, or thin handle of a wooden spoon, poke 15-20 holes into cake. Set aside.
In a small bowl, mix sweetened condensed milk, coconut milk, and lime juice. Pour mixture slowly and evenly over warm cake, filling holes and spreading into the corners with a spatula. Let the cake finish cooling for 15 minutes, cover and refrigerate overnight or until well chilled.
To make Whipped Cream Topping: in a medium bowl, beat cream, sugar, and vanilla with an electric mixer until soft peaks form; spread over top of cooled cake. Garnish with additional lime zest and serve. Store leftover cake in the refrigerator for up to four days. The whipped cream topping may fall slightly but will still taste delicious
Notes: Key limes or regular Persian limes work well in this recipe.