Salt the water like the sea. Bring a large pot of water to a boil and season it generously with salt.
This is the first and best chance to flavor your pasta from the inside out.
Cook the pasta to just shy of al dente. Add the pasta and cook according to package directions, but stop 1–2 minutes early. You’ll finish it in the sauce. Before draining, save 1 cup of pasta water.
Start the sauce base. In a large skillet over medium heat, melt the butter with the olive oil.
Add the minced garlic and cook 30–60 seconds until fragrant. Don’t brown it; garlic burns fast.
Pour in the cream. Stir in the heavy cream and bring it to a gentle simmer. Let it bubble softly for 2–3 minutes to thicken slightly.
Season with salt, black pepper, and red pepper flakes if using.
Add Parmesan off the heat. Turn the heat to low and gradually whisk in the Parmesan until melted and smooth. If the sauce looks too thick, loosen it with a splash of pasta water.
Combine pasta and sauce. Add the drained pasta to the skillet and toss well to coat. Drizzle in more pasta water, a little at a time, until the sauce becomes glossy and lightly coats every piece.
Finish with brightness. Add lemon zest and a squeeze of juice (start small).
Taste and adjust salt and pepper. The lemon lifts the richness without making it sour.
Serve hot. Plate the pasta and top with extra Parmesan and chopped parsley. Enjoy right away while it’s silky and smooth.