Melt butter in a medium saucepan over medium-high heat. Add 3 cups (750 mL) of the spinach and cook until it wilts completely. Add remaining spinach and cook until wilted. Turn off heat and stir in lemon zest and juice and ¼ tsp (1 mL) of salt. Season with fresh pepper to taste.
Place linguine in a large, wide saucepan. (It should be able to lie flat, but it doesn’t have to be in a single layer.) Add enough cold water to cover linguine by about 1 inch (2.5 cm). Add remaining salt and place pan over high heat. Stir with tongs every now and then. Once it comes to a boil, keep stirring until pasta is just tender. (The whole process should take about 15 minutes.) As soon as it is barely tender, use tongs to transfer pasta directly to pan with spinach mixture.
Turn heat to medium and stir to incorporate spinach mixture with pasta. Serve immediately, topped with grated Parmesan.
Nutrients per serving: 384 calories, 15 g protein, 12 g fat (6 g saturated fat), 56 g carbohydrates (4 g fibre), 32 mg cholesterol, 643 mg sodium
Best Health tip: When pasta is stripped down like this, it’s even more important to use the best-quality dried pasta you can find.