Heat oven to 450 degrees
Place coconut oil in 9 inch oven proof cast iron skillet.
In small bowl, combine egg, pineapple, sugar, vanilla, chiles, yogurt, and buttermilk. Blend until thoroughly combined. Set aside.
In large bowl, combine remaining dry ingredients and mix.
Mix liquid mixture into dry mixture and stir about 20 strokes.
Remove skillet from oven and carefully pour in batter.
Bake 18 - 21 minutes until light golden brown and knife inserted in center comes out clean.
Remove from oven and brush with butter. Slice and serve warm.