Boil water. Fill a large pot ⅔ of the way with water and bring it to a boil. While the water is coming to a boil:
Make the pesto. Add all ingredients for easy nut-free pesto into a food processor or blender. Blend about one minute, until it's pureed but still has a little texture. (Alternatively you can use your favorite store-bought pesto.) Set pesto aside.
Cook the pasta. Once the water is boiling, add pasta and cook until it's al dente. While the pasta is cooking:
Blister the tomatoes. Heat olive oil in a large pan or cast iron skillet over medium-high heat. When the olive oil is fragrant, add the tomatoes. Let the tomatoes sit for two minutes, until they start to blister. At that point, turn off the heat, add the balsamic vinegar, give the tomatoes a quick stir, and let them sit another two minutes. When done, season with salt and pepper.
Reserve starchy pasta water. When the pasta is al dente, reserve ½ cup of starchy pasta water to help create the finished pasta dish. Then drain pasta.
Toss everything together. Add the drained pasta and the pesto to the large pan of blistered tomatoes (reserving a few tomatoes to use as garnish, if desired). Add two tablespoons of pasta water and toss all ingredients together. If needed, add additional pasta water until you achieve your desired consistency.
Garnish & enjoy. Serve pasta al pesto and (if desired) garnish with reserved blistered tomatoes, torn basil leaves, and freshly grated parmesan cheese. Enjoy!