Bring a large pot of salted water to boil for the pasta. In a large skillet over medium heat, heat the olive oil and add the onions. Cook until translucent. Add the tomatoes and salt and pepper.
Cook for 10 – 15 minutes, until slightly wilted.
Place the ricotta in a mixing bowl. With a wooden spoon, whip together with salt and pepper until creamy.
Cook the pasta until al dente, drain it, and add it to the skillet with the tomatoes. Cook together for about a minute. Mix in the ricotta. Serve immediately,