In a medium saucepan, heat ¼ cup of high-quality extra virgin olive oil over medium heat. Add 3 cloves of minced garlic, a pinch of red pepper flakes, and a few fresh basil leaves. Allow the mixture to simmer gently for about 3–5 minutes until fragrant and lightly golden.

In another skillet, melt 4 tablespoons of butter over medium heat. Once bubbling, add a halved onion, cut side down, and cook until deeply caramelized, about 8–10 minutes.

Once the onion is caramelized, remove it from the pan and set aside. Pour in 1 can of San Marzano tomatoes, crushing them slightly with a spoon. Allow the sauce to simmer for 15 minutes.

Strain the infused oil from the garlic and basil into the simmering sauce, discarding the solids. Stir thoroughly to combine.

Boil a pot of salted water and cook 12 ounces of spaghetti until al dente, about 8–10 minutes. Drain the pasta, reserving a bit of the starchy water. Add the spaghetti to the sauce and toss well.

Plate your spaghetti, garnishing with fresh basil leaves and a drizzle of the reserved infused oil.