Blanch the tomatoes and once drained, peeled and deseeded place pass them in a vegetable mill. Rinse the basil and chop it. Grate some of the ricotta and slice the rest into flakes. Heat the oil in a pan, add the tomato pure, the salt, the sugar and simmer for 15 minutes over a high heat mixing with a wooden spoon.When it is almost ready add the basil. Then cook the pasta in a large pan with plenty of boiling water, drain it and toss it in the pan with the sauce add the grated hard ricotta, mix it well, sprinkle with the ricotta flakes and serve.