Preheat oven to 375 degrees F and thoroughly grease a 9-inch springform pan.
In a small microwave safe bowl, add butter and milk. Heat until butter is fully melted and stir to combine, then set aside.
In a large bowl, mix eggs and sugar until light and airy, then add vanilla. Add flour, baking powder, and salt and mix until just combined. Gently mix in butter-milk mixture.
Transfer batter to the prepared pan and bake for 25-30 minutes, or until top has set. Start on coconut topping as it bakes.
Topping: Add butter, brown sugar, and milk to a small saucepan over medium heat. Cook for 2-3 minutes or until it reaches a simmer. Remove from heat and mix in vanilla and coconut.
Remove cake from the oven at the 25-30 minute mark and pour coconut topping over the top. Spread into an even layer.
Increase oven temperature to 400 degrees F and bake for another 8-10 minutes until coconut begins to turn golden.
