1. Preheat oven to 325 degrees F. Line a standard 12-cup cupcake tin with paper baking cups.
2. Mix together the rice milk and apple cider vinegar in a 2-cup measuring cup.
3. Whisk together the flour, cacao powder, baking powder, baking soda, guar gum and salt in a large bowl. Make a well in the middle.
4. Add the grapeseed oil, coconut nectar, vanilla and stevia to the flour mixture and stir to combine. Next add the rice milk mixture and stir until the liquid is absorbed and the batter is smooth. Stir in the yogurt until well combined.
5. Pour the batter into the measuring cup, as the spout will make it easier to pour the batter into the cupcake tin without spillage.
6. Pour the batter into the prepared cupcake tin, dividing it evenly. Each cup should be about two-thirds full. Bake the cupcakes for 16 to 17 minutes, or until they bounce back slightly to the touch. Rotate the cupcake tin from front to back after 10 minutes of baking.
7. Transfer the cupcake tin from the oven to a wire rack and let sit for 10 minutes before removing the cupcakes to cool completely.Chocolate Frosting
8. Mix together the coconut nectar, coconut oil and mashed avocado in a large bowl. Add the powdered erythritol, cacao powder, warm water, stevia and salt and stir until smooth and well combined.
9. Frost the completely cooled cupcakes.
10. Keep unfrosted cupcakes in an airtight container for up to 3 days, or wrap and freeze them for up to 3 months. Leftover frosting keeps in the fridge for about 4 weeks if stored in an airtight container.