Preheat oven to 350F. Add the flour, baking powder, oat fiber and salt to a bowl and whisk together, then set aside.
Separate the eggs, and set yolks aside. Whip up the egg whites until you have soft peaks. Add the sour cream, lemon juice, lemon zest and vanilla extract to the egg yolks and mix.
Add in the swerve and continue mixing. Then add in the egg whites and quickly mix just to combine. Add the dry ingredients into the wet and mix by hand.
Scoop into a silicone muffin pan, silicone cupcake liners or paper liners. Bake for 15 minutes.
To Make the Meringue Topping
While the cupcakes are baking, add the egg whites and cream of tartar a large mixing bowl (or stand mixer) and whip to soft peaks. Then slowly add the swerve while mixing to stiff peaks.
Transfer the mix to a piping bag fitted with the tip of your choice. If you don't have piping tips, you can add to a food storage baggie, cut a hole at the tip and pipe on that way.
To Finish the Cupcakes
Increase oven temperature to 400F. Add the lemon curd filling into a piping bag fitted with a large round rip. Gently push the tip into the center of the cupcake and squeeze a little of the filling into it.
Pipe the meringue over the top of the cupcakes, as if you were frosting them. Place them back into the oven on the upper 2/3 rack and bake for 3-4 minutes or until the meringue is toasted. Do not over-bake!! If they bake too long, the tops will be more like meringue cookies, and not a little gooey inside. You want them just barely toasted on the outside.
The Oat Fiber is important in this recipe, as it gives a great bread-like texture. I use Lifesource Foods Oat Fiber 500, because it’s ground to a fine powder and has a very mild flavor.Oat Fiber is not the same as Oat Flour, which is made from grinding oats. Oat Fiber is made from grinding the outer husks of oats and is pure insoluble fiber. Insoluble fiber does not dissolve in water and is not broken down in the digestive tract, so it’s Low Carb and Keto friendly.