Preheat oven to 325º F. Line a 9×5 loaf pan with parchment paper. I first spray it with oil, then add the parchment, to help it stick to the pan, and then press the paper firmly against the edges. Set prepared pan aside.
Add fresh egg whites, cream of tartar, monk fruit sweetener, and salt to a standing mixer bowl with the whisk attachment. Whisk on medium speed until the egg whites are foamy, then turn it on high speed until the egg whites form very stiff peaks. The egg whites should stay in the bowl when the bowl is turned upside down!
Add the egg white protein powder, and mix in on low. (See notes about removing clumps from egg white protein.)
Add the egg white mixture to the lined loaf pan. Use a spatula to pile the egg whites into a bread loaf shape.
Bake the bread for 33 minutes, until the top is very golden brown.
Allow to fully cool before slicing the bread.