Preheat oven to 450 degrees. Spread out tomatoes on a small baking sheet. Add garlic. Drizzle with a little bit of olive oil, about 1 tablespoon, to lightly coat tomatoes and garlic. Sprinkle with salt and pepper. Roast in oven until tomatoes are soft, skins begin to wrinkle, and a few start to burst, about 20 minutes.
While tomatoes roast, toast walnuts in oven on a small baking sheet until they begin to turn golden brown and fragrant, about 5-10 minutes.
Add roasted tomatoes, garlic, any juices from the baking sheet, and the toasted walnuts to a food processor. Add in Parmesan, basil, salt and pepper to taste, and about a tablespoon olive oil. Pulse until sauce begins to look smooth. If necessary, add another tablespoon or so of olive oil at a time while pulsing until the sauce is smooth and to desired consistency.
To serve with pasta:
Cook 1 lb. of pasta according to package directions. Drain, reserving about ½ cup of pasta water. Toss the pesto sauce with the hot, cooked pasta, adding a little pasta water to thin the sauce and coat the pasta. Serve warm.
Notes
For the freezer: freeze sauce in small portions in small ziplock bags. Defrost in fridge when ready to use.
Recipe by Wright Family Table at https://www.wrightfamilytable.com/roasted-cherry-tomato-pesto-sauce/