Preheat your oven to 350 degrees F. Line 6 muffin pan cavities with foil liners and lightly grease the liners.
In a large bowl, whisk the eggs, oil, vanilla, and stevia.
Add the almond flour and whisk it in thoroughly until the batter is very smooth.
Whisk in the salt and baking powder.
Divide the batter between the cupcake liners. The batter will be fairly thin.
Bake the cupcakes until puffed and a toothpick inserted in their center comes out clean, 15-17 minutes.
Place the pan on a cooling rack for 5 minutes, then remove the cupcakes from the liners and place them directly on the cooling rack. Cool completely, about 1 hour, or place in the fridge to cool quickly (should take about 20 minutes in the fridge).
If your cupcakes have an uneven dome, gently shave it off before frosting, as shown in the video below.
To make the frosting, place the softened unsalted butter, heavy cream, cocoa powder, vanilla, and stevia in a medium bowl. Using a handheld electric mixer, beat on low to incorporate, then beat on medium for about 1 minute, until the frosting is light and fluffy.
Spoon the frosting on top of the cupcakes and gently spread it. Or use a piping bag to pipe it onto the cupcakes.
* A granulated sweetener in the frosting will feel grainy - so please use a powdered sweetener. If using a powdered sweetener in the frosting instead of stevia, it's possible that you would need to add a bit more heavy cream to get the right consistency.