Cook macaroni according to least amount of time on package. For example, if it says boil 8-10 minutes, do 8. Drain and immediately rinse under cold water to stop cooking. Set aside.
Preheat oven to 425°F.
Place milk in a microwave-safe bowl and microwave for 2 minutes.
Meanwhile, in a medium pan over medium heat, melt butter.
Add flour to butter and whisk constantly, 2 minutes. We're making a Roux Paul, y'all!
Grab warm milk from microwave and add to flour/butter. Whisk frequently just until mixture starts to thicken, about 5 minutes.
Take off heat and stir in cheeses.
Add macaroni, lemon zest, ground mustard, and a dash of nutmeg and cayenne. Taste and then adjust with salt and pepper.
Place in greased 1.75 quart Pyrex (linked below).
If you like a looser, soupier mac and cheese, add warm milk little by little (stirring between adds) until desired consistency is reached. Adding cold milk will make the mixture seize and tighten. Keep in mind, consistency will always tighten a bit once baked. Taste again in case salt and pepper need to be adjusted. Cover surface of mac and cheese with panko or Ritz and spray topping evenly with cooking spray.
Bake uncovered for 15-20 minutes or until toppings are a sensual golden-brown.
Serve immediately! ENJOY!