Bring a large pot of water to a boil, add pasta, and cook for 7-9 minutes or until al dente. Reserve ¼ cup of pasta cooking water before draining.
In a skillet, heat olive oil over medium-high heat. Add onions and cook until translucent (2-3 minutes).
Add garlic, tomatoes, and oregano, cooking for 5-6 minutes until tomatoes burst and release their juices.
Mash the burst tomatoes with a spoon or fork to release more juices. Cook for 1-2 minutes.
Transfer the tomato mixture to a blender. Add ricotta cheese and blend until smooth.
Pour the sauce back into the skillet. Add the drained pasta and stir to combine. Adjust consistency with reserved pasta water if needed.
Season with salt and pepper. Garnish with fresh basil and serve immediately.
