Melt butter and olive oil in a large heavy pot over medium-low heat. When butter is melt, add sliced and crushed garlic and red pepper flakes until they are fragrant. Stir occasionally to make sure garlic and red pepper flakes don’t get burnt.
Once they are fragrant, add sliced onion and broccoli florets. Season them with salt and pepper. Toss everything until onions are translucent and florets are tender but still firm, for 3-4 minutes. Add lemon zest at the end and quickly toss everything again until it’s fragrant.
Add whole milk to the pot with salt and garlic powder and let it simmer over medium heat for 5 minutes.
Meanwhile, cook pasta, occasionally stirring, until very al dente (2–3 minutes less than package directions). Reserve 1/2 cup of pasta water.
Using tongs, add pasta to milk broth. Cook everything over high heat and bring everything together with pasta water and Parmesan for a minute, or until the pasta is cooked when you taste, “al dente” if you can.
Serve pasta with freshly cracked black pepper and more grated Parmesan cheese.
Notes
Pro tip: don’t overcook your broccoli – not only does the texture become soft and bland but it loses nutritional value.