Boil the pasta. Bring a large pot of salted water to a boil.
Add noodles and cook until al dente according to package instructions. Scoop out at least 1 cup of pasta water before draining.
Melt the butter. In a large skillet over medium heat, melt 3 tablespoons of butter. Save the last tablespoon for finishing.
Soften the garlic. Add the minced garlic to the melted butter.
Cook for 30–60 seconds, stirring often, until fragrant. Do not brown the garlic or it will taste bitter.
Build the sauce. Pour in 1/2 cup of reserved pasta water and bring to a gentle simmer. Whisk to emulsify the butter and water into a silky sauce.
Toss the pasta. Add the drained noodles to the skillet and toss well. Sprinkle in the Parmesan gradually, tossing until melted and glossy.
If the sauce seems tight, add a splash more pasta water.
Finish for flavor. Stir in the remaining 1 tablespoon of butter, chopped herbs, and lemon juice (if using). Season with salt, plenty of black pepper, and red pepper flakes if you like a little heat.
Serve immediately. Top with extra Parmesan and a final crack of pepper. Eat while warm and creamy.