Cut the tomatoes, onion and garlic in half, then put them in a baking dish (facing upwards). Drizzle or spray with oil and season with salt and pepper.
Put the tray in a preheated oven (temperature set to 180°C), and roast for approx. 30 minutes until the vegetables are tender. Set aside.
Discard the skin of the onion ang garlic cloves, then put their flesh into a saucepan. Add the tomatoes and the roasting jus too.
Roughly cut the broccoli (including the stem) into chunks, add these to the pan, then pour in the stock. Bring to the boil and cook for 10-15 minutes, until the broccoli is cooked through.
Turn off the heat and add the parsley. Using a stick blender, whiz the soup until you get a smooth or textured soup (depending on your liking).
Serve with a squeeze of lemon juice.