Fill a large pot with water, salt it generously, and bring it to a rolling boil over high heat. Salting the water properly is what seasons your pasta from the inside, not just the sauce. Get this going first so both components finish around the same time.
In a large nonstick skillet, warm the olive oil and butter together over medium heat. Add the cherry tomatoes, cover the pan, and let them cook for about 5 minutes until they begin to burst and release their juices. This step builds the base of your sauce.
While the tomatoes are cooking, drop your penne into the boiling water and cook until al dente, following your package instructions. Before draining, scoop out about half a cup of the starchy pasta water and set it aside. This water is key for a glossy, clingy sauce later.
While everything simmers, mince your garlic cloves finely and roughly chop your fresh basil leaves. Having these ready means you can add them at exactly the right moment without slowing down the cooking process.
Uncover the skillet and gently press the tomatoes with a fork to release even more of their juices. Stir in the minced garlic and cook for about a minute until fragrant. Add the salt, pepper, chili flakes, and thyme, then pour in the pureed tomatoes. Bring the mixture to a gentle boil and let it simmer for two minutes to deepen the flavor.
Lower the heat and stir in the ricotta and Parmesan until they melt into the tomato base, creating a smooth, creamy sauce. Fold in the chopped basil for a fresh, herby lift right before you add the pasta.
Add your drained penne straight into the skillet along with the reserved pasta water. Toss everything together until the pasta is fully coated and the sauce turns glossy. Taste and adjust the salt if needed, then serve immediately while it's warm and creamy.