Bring a pot of water to a boil, add salt, and drop the penne in. Cook until it's before al dente (about 2-3 minutes before it's done cooking, remove it from the pot and place it into the sauce – it will finish cooking in the sauce)
While the water is boiling/pasta is cooking, heat olive oil in a pan. Add the onion along with and sauté until onion is tender, about 3-5 minutes.
Add the halved cherry tomatoes, the basil, and season with salt, and cook down until burst, and they release their juices, about 8-10 minutes.
By this time, the pasta should be ready to add to the pan. Add the penne to the pan, along with a ladle of pasta water.
Continue to cook the pasta in the pan until the pasta water is absorbed and it is al dente. If it needs more time to cook, add more pasta water.
Add the ricotta to the pan, and stir everything together. Add pasta water if needed. Sprinkle in parmigiano reggiano and mix one more time. Plate and top with more parmigiano reggiano if desired!