- Reserve pasta water for later
- Remove seeds and core from beefsteak tomato and chop into large pieces
- Pulse with garlic, salt, and chili flakes until smooth
- Transfer to bowl and mix cherry tomatoes, olives, olive oil and capers
- Add pasta, basil, and butter. Toss with pasta liquid until sauce coats spaghetti.
- Chill for 1 or 2 hours to allow flavors to meld