Select a saucepan that can hold the bowl of your stand mixer easily. Fill it with a few inches of water and bring to the simmer.
Crack eggs into the mixer bowl, add sugar, and salt.
When water is hot, place eggs over, and beat with a whip until they are golden and warm. Note: As long as the water is not too hot, it is okay to leave the egg and sugar mixture sitting there without it being stirred, the point of this is to melt the sugar, and warm the whole, but do not leave it out of sight, whip it periodically, this may take 7 minutes. The mixture should be warm on your finger, but not hot.
Transfer the bowl to the mixer and fit with the whisk attachment. Turn to setting 8 (out of 10), and beat until the eggs almost fill the bowl. This may only take 5 minutes.
Tip the butter in gently, still with the mixer on high speed, let it run down the sides of the bowl. The mixture should deflate only minimally, if at all.
Remove the mixing bowl from the stand, discard the whisk attachment.
Get a whisk, it could be the one that was used to whip the eggs in the water, or it could be a clean one. Also have hand a rubber spatula or big wooden spoon.
Add the flour in thirds. Whipping lightly but well between additions. The mixture will deflate but do not be alarmed, there will be plenty of batter, and the cake will still be light. Do not overwork the dough.
Switch to the spoon, lifting the batter up several times to assure that there are no lumps. Be cautious to overwork the batter.
Transfer to pans evenly and rap them against the side of the counter.