Bring a pot of salted water to a boil while measuring the remaining ingredients. Having everything ready keeps the garlic and roux from overcooking while you search for an ingredient.

Add the ziti rigati to the boiling water as you begin the sauce, then cook according to the package directions without overcooking. Drain when the pasta is firm al dente so it can finish absorbing flavor in the sauce.

Warm the butter in a skillet over medium-low heat for about 2 minutes, then add the minced garlic and swirl the pan occasionally. Continue until the butter foams and lightly browns around the garlic without letting it scorch.

Raise the heat to medium and whisk in the flour, cooking it for about 2 minutes. The roux should deepen slightly in color and smell toasted rather than like raw flour.

Whisk the chicken broth into the roux in small additions, stirring continuously after each splash. The mixture should become smooth and gradually thicken without lumps.

Pour in the half and half slowly while stirring the sauce. Keep the sauce moving until it looks creamy and even throughout.

Stir in the dried oregano, parsley, mustard powder, garlic powder, and lemon juice. The lemon should brighten the aroma without making the sauce taste sharply acidic.

Turn the heat to low, then stir in the Parmesan followed by the spinach. The cheese should melt smoothly and the spinach should collapse into the warm sauce.

Add the drained pasta and toss it through the sauce until evenly coated. Let it rest briefly as the sauce settles into a thicker, silky coating.