Heat the chicken broth in a saucepan just until hot, but not simmering.
Peel and chop the onion, and melt the butter in a 4 quart saucepan over medium heat, taking care not to let it brown. Add the onion to the butter and sauté, stirring constantly.
When the onion has softened, add the rice and continue cooking, stirring constantly, for about three minutes. Use a ladle to scoop up about a half cup of broth and add it to the rice mixture. Stir thoroughly. As the rice absorbs the broth, add another ladle of the broth to the rice mixture.
While the risotto is cooking, heat 2 tablespoons of olive oil in a skillet over medium high. When the oil is hot, add the tomatoes and sprinkle them with salt and pepper.
Continue to add broth gradually to the rice mixture as it is absorbed. This will take about twenty minutes. Test to see whether the risotto is cooked. The individual grains should have some "tooth" or texture to them, but they shouldn't be at all crunchy. If you run out of broth, either heat some more or switch to water.
When the rice is done cooking, add the cooked tomatoes, the chopped basil, and the Parmesan cheese. Cover and allow it to sit for about five minutes, then serve piping hot.