Step 1

Bring a large pot of salted water to boil. Cook spaghetti until firm to the bite (al dente), about 8 minutes. Drain, reserving 1 cup of pasta water.

Step 2

Meanwhile, heat olive oil and butter in a large skillet over medium heat until sizzling. Add minced garlic and red pepper flakes; cook and stir until fragrant, about 30 seconds. Remove from heat.

Step 3

Once you've drained the pasta, set skillet with the garlic mixture over medium heat. Add drained, cooked pasta and 1/4 cup of reserved pasta water; toss to coat. Cook and stir until heated through, adding more pasta water if pasta seems too dry.

Step 4

Remove pasta from heat and stir in lemon zest and juice, and parsley. Season to taste with salt and pepper. Transfer to serving bowl or platter; top with grated parmesan cheese and serve.