Preheat the oven to 325°F (165°C). Line an 8 × 4-inch loaf pan with parchment paper.
Pour the room-temperature liquid egg whites into a clean, dry mixing bowl. Beat on medium speed until foamy.
Increase the mixer speed to high and continue beating until soft peaks form.
Slowly sprinkle in the egg white powder while mixing. Add it gradually to prevent clumps.
Continue beating until stiff peaks form. The mixture should be thick, glossy, and airy.
Gently spoon the mixture into the prepared loaf pan. Smooth the top without pressing out the air.
Bake for 35–40 minutes, or until the loaf is fully set and the center reaches about 160°F (71°C).
Turn off the oven and leave the bread inside with the oven door slightly open for 10 minutes.
Remove the loaf from the pan and allow it to cool completely before slicing.
Slice with a serrated knife. Lightly toast the slices before serving for the best texture.