Melt the butter in a 2-quart sauce pan over medium-high heat. Press the garlic and add it to the melted butter, stirring a bit. Let it cook for 30 seconds, being careful not to let the garlic burn.
Lower the heat to medium and stir the cream into the garlic mixture. Add the salt and pepper and stir to combine.
Let the cream come to a low boil, while stirring frequently.
Then lower the heat and let the pot simmer, stirring frequently, for 8-10 minutes, or until the cream thickens. It should be thick enough to coat the back of a spoon.
Turn off the heat and move your Alfredo pot to a cool burner. Gradually stir in the freshly grated Parmesan and Romano.
Place the pot over low heat and stir until the sauce is thickened further. It is done when you push your spoon along the bottom of the pan and can see the bottom of the pan. It will take a few minutes.
The sauce will thicken even more as it sits. It's best to make the sauce and use it immediately, because Alfredo sauce doesn't reheat well. It separates and curdles.
Serve the garlic Alfredo sauce with fettuccine, zoodles, or on pizza or chicken, etc. Once mixed with pasta, you can store leftovers in the refrigerator for up to four days. To reheat fettuccine Alfredo, drizzle on a little olive oil before microwaving it, so the pasta isn't dry.
It's important to use freshly grated Parmesan and Romano, so the cheese will melt smoothly. (Don't use the cheese sold in a can, or the sauce will be grainy.)This sauce makes enough for one pound of pasta. You can easily cut the sauce recipe in half for 8 ounces of pasta. Note that your sauce will take less time to come to a boil and thicken.