Preheat the oven to 350°F (180°C) and grease a 10” skillet or 9”x5” baking dish.
In a medium sized mixing bowl combine the almond and coconut flour with the flaxseed baking powder, and a pinch of salt. Fold in ¼ cup of the shredded cheddar cheese.
In another mixing bowl, beat the eggs with an electric mixer until fluffy and pale yellow. Add the butter, heavy cream, and apple cider vinegar. Whisk again to combine for just a few seconds.
Combine the flour mixture with the egg mixture and whisk until fully incorporated.
Pour into the prepared baking dish and top with the remaining cheese.
Bake for about 30 minutes until a skewer comes out clean.
Allow to cool before removing from the pan, slice and serve.