In the bowl of a stand mixer fitted with a dough hook or a large bowl, combine the flour and salt.
Mix in the eggs and knead to bring the dough together. Only add water if absolutely needed after a few minutes of kneading.
Once smooth, wrap the dough in plastic or place in a covered bowl and allow to rest for 30 minutes.
Divide the dough in half. Keep one wrapped and place the other on a lightly floured surface.
Roll the dough by hand with a rolling pin or use a pasta machine, flouring the dough as needed to prevent sticking. Roll until about 1/16 inch (1.5 millimeters) thick or to the thinnest setting on the pasta machine.
Cut the rolled out dough using the fettuccine attachment on the pasta machine or loosely roll up and use a sharp knife to cut the noodles into 1/4 inch (6 millimeters) wide ribbons.
Unroll the noodles and separate to prevent sticking. Arrange in a single layer on a parchment lined baking sheet. Repeat with remaining half of dough.
In a small bowl, combine the cocoa powder and powdered sugar.
Bring a large pot of salted water to a boil. Add the noodles, in batches if needed to avoid overcrowding, and cook until they rise to the surface and are just tender, 1-2 minutes. Drain.
In a large pan, melt the butter over medium heat.
Remove from heat once melted and toss in the drained noodles.
Arrange among serving dishes and top generously with the cocoa sugar mixture.
Serve immediately.