Spaghetti with Mascarpone, Meyer Lemon, Spinach, and Hazelnuts

Baby spinach or coarsely chopped regular spinach, loosely packed

Meyer lemon, zest of medium

Meyer lemon, Juice of medium

Spaghetti, dry

Black pepper, Freshly ground

Kosher salt

Nutmeg

Hazelnuts, toasted

Mascarpone cheese