Heat the clarified butter in a skillet over low heat, and place the quince wedges into the pan. Cover, then gently cook the quince wedges until softened, about 15 minutes. Remove from heat and set aside.

Mix the flour, white sugar, and salt in a bowl. In a separate bowl, mix the beer with the vanilla extract and lemon zest; gradually mix the flour mixture into the beer mixture until it becomes a smooth batter.

Melt the coconut oil in a skillet over medium heat. When the oil is hot, dip the quince wedges into the batter and place them in the hot oil; fry in batches until golden brown. Remove fried quinces to a warm platter while you finish frying. Sprinkle the fried quinces with demerara sugar to serve.