Bring water to a boil, and cook macaroni per package instructions
Bring water and sodium citrate to a simmer over medium heat.
Slowly incorporate the cheese a little at a time while pulsing an immersion blender to form a cheesy emulsion.
Notes
Had 2 pints left over, and added 1 pint of peas (frozen, added 1/4 cup water, microwaved for 3 minutes on high, strained). Would've been good with tuna as well.
I didn't really care for the serious eats version. It was okay, but there was too much or too liquidy of a sauce for it to be a stove top mac and cheese, and it had to be baked.