Put basil leaves, parmesan cheese, vinegar, lemon, garlic, lemon zest and salt/pepper in a blender. Blend. Pour 1/2 cup of olive oil slowly into the blender via the top attachment. Serve once smooth.
Instructions for the salad:
Cook pasta according to directions. Pour cold water over pasta after draining and stir into a large bowl. Add in the cherry tomatoes, mozzarella, red onion, and salt and pepper. Stir in the basil pesto vinaigrette. Evenly incorporate. Serve cold.
If you want to make this dish even more festive for Memorial Day Weekend, add 4-5 drops of blue food coloring to the boiling water for the pasta. The more food coloring you use, the darker blue the pasta gets. Or just serve in a big blue bowl:).