Bring a pot of water to the boil, add a liberal amount of salt to it and cook pasta in water till al dente (according to packaging directions).
Whilst pasta is cooking, combine all the Spinach Basil Pesto ingredients in a food processor and process till almost smooth. Taste and season accordingly.
To make Cherry Tomato and Red Onion sauté, in a saucepan, heat olive oil up. Add onions and lightly sauté red onion over a low heat until it goes translucent, about 5 minutes. Add cherry tomatoes to the pan and lightly sauté for half a minute, then take entire pan off the heat. Season with salt and pepper.
Once pasta is cooked, drain and set the cooking water aside. Combine drained pasta with Basil Spinach Pesto and add a little amount of the reserved cooking water to loosen the pesto up. Toss well to combine.
Serve topped with Cherry Tomato and Red Onion sauté.