Heat the oven to 180°C/Fan 160°C/Gas 4. Peel and finely chop the onion. Peel and grate or crush the garlic. Fill the kettle and boil it.
Rinse the tomatoes. Pop them on a baking tray. Drizzle with olive oil. Season with salt and pepper. Roast in the oven for 15-20 mins or till softened and charred at the edges. Keep warm at the bottom of the oven.
Warm a drizzle of olive oil in a pan. Add the onion. Season. Stir and fry over a low heat for 6-8 mins till soft and glossy but still pale.
Add the garlic and the risotto rice to the onion. Cook for 1 min. Keep stirring. Crumble the stock cube into a jug filled with 700ml hot water from the kettle. Stir till it dissolves.
Gradually add the stock to the risotto rice, a splash at a time. Cook over a low-medium heat till each splash of stock has been absorbed before adding more. Stir often. The rice should be tender and creamy.
While the risotto cooks, warm a dry frying pan over a low heat. Tip in the pine nuts. Toast 2-3 mins till golden brown. Put to one side. Rinse the watercress. Pick out any large stalks. Pat dry with kitchen paper.
Ladle the risotto into warm bowls. Top with the roast tomatoes, watercress and spoonfuls of ricotta. Scatter with the pine nuts.