Halve the tomatoes and scoop out the seeds into sieve placed over a bowl. Press the seeds with a spoon to extract all the juice. Set aside.

Grill the tomatoes skin-side up until the skins are evenly blackened and blistered. Rub off the skins and dice the flash.

Melt the butter in a large frying pan and cook the onion for 5 minutes until beginning to soften.

Add the tomatoes, the reserved juice and seasoning, then cook, stirring occasionally, for about 10 minutes. Meanwhile, bring the vegetable stock to the boil in another pan.

Add the rice to the tomatoes and stir to coat, then add a ladleful of stock and stir gently until absorbed. Repeat, adding a ladleful of stock at a time, until all the stock is absorbed and the rice is tender and creamy.