Vegetarian ‘Carbonara’ with Spinach

Heat the oil in a large nonstick skillet over medium heat. Add the onion and garlic and cook, stirring occasionally, until light golden, about 5 minutes.

Meanwhile, cook the pasta in a pot of salted boiling water until al dente. Reserve 2 cups cooking water and drain the pasta. Return the pasta and reserved cooking water to the pot and heat over low. Add the butter and onion-garlic mixture and cook, stirring constantly, until most of the liquid is absorbed and sauce is slightly thickened, 3 to 5 minutes. Add the spinach, season with salt, plenty of pepper and red-pepper flakes, if using, and stir until spinach is wilted. Stir in the Parmesan and lemon juice; season with salt and pepper.

Divide the pasta among 4 bowls and top each with 2 tablespoons smoked cheese. Finish with more black pepper, if desired.