Dice the onion relatively small and mince or finely chop the garlic. Peel the tomatoes (place in a bowl with boiling water, leave a minute or two then pierce - the skin should separate and start to peel back when ready. Remove from the water and peel off and remove skin). Dice the tomatoes and remove the core. Remove roughly half of the seeds but keep all the juices and rest of the tomato.
Heat the olive oil in a wide pan which has a lid over a medium heat and add the onion. Cook, stirring regularly until softened, around 3-4 minutes, then add the garlic. Cook for a minute more, stirring now and then. Add the tomatoes, bring to a simmer then reduce the heat and simmer for around 5 - 10 minutes so the tomatoes become very soft.
Add the rice and cook briefly to ensure the grains are well coated. Add the wine and deglaze - stir and scrape the bottom of the pan to remove any browning and mix into the rice (it adds flavor!). Cook and stir so the liquid is largely gone.
Add the stock all at once, season with salt and pepper as needed (this will depend how much your stock is seasoned already) and add the bay leaf. Cover the pan and bring the mixture to a simmer. Once simmering, reduce the heat so the mixture simmers and cooks without boiling too strongly. Leave to cook roughly 15 minutes until the rice is cooked through.
Once the rice is cooked, remove the lid and if you like, continue to cook to reduce the liquid if you like (you can serve it wither slightly soupy or drier, as you prefer). Check the seasoning and adjust if needed and remove the bay leaf. Add the butter and stir so that it melts and gently coats the roce.
Serve topped with freshly chopped parsley.
Video
Notes
I highly recommend using homemade stock, if at all possible. If you don't have good fresh tomatoes, you can also use canned/tinned or tomato passata instead.