Start by bringing a large pot of water to boil for your pasta – you want the water to be as salty as the sea. This is the perfect time to prep your ingredients while the water heats up.

Heat olive oil in a large, deep skillet over medium heat. Add your diced onion and cook for about 5-6 minutes, until they’re soft and translucent but not browned. You’ll know they’re ready when they look glossy and you can easily squish one against the pan with your spatula.

Add the minced garlic and cook for just 30-45 seconds, stirring constantly. You’ll smell the garlic become fragrant – don’t let it go longer or it’ll brown and get bitter.

Pour in both cans of diced tomatoes, juice and all. Give everything a good stir, then bring to a gentle simmer. Let this cook for about 15 minutes, stirring occasionally. The sauce should thicken slightly and the tomatoes will break down a bit – you’ll notice the color deepen to a rich red.

While your sauce simmers, cook your penne in the boiling water until it’s just barely al dente – usually about 1 minute less than the package directions. The pasta will finish cooking in the sauce. Save a cup of pasta water before draining!

Lower the heat under your sauce to medium-low and stir in the heavy cream. Let it simmer gently for 2-3 minutes until the sauce turns a beautiful peachy-pink color and thickens enough to coat the back of a spoon.

Add the butter and stir until it’s completely melted into the sauce. This makes everything extra silky and helps the sauce cling to the pasta better.

Add your drained pasta to the sauce along with the torn basil leaves, salt, black pepper, and red pepper flakes if using. Toss everything together well – if the sauce seems too thick, add a splash of that reserved pasta water to loosen it up.