At least a day ahead, prick the tomatoes all over with a fork, to ensure they drink up the luscious marinade.
In a large bowl, whisk all the marinade ingredients with half a teaspoon of salt, then drop in the tomatoes, toss gently to coat, cover and leave to sit at room temperature for a day or two (if it’s hot outside, a day should be plenty), turning them regularly.
On the day you want to serve, gently pulse the butter beans with the liquid from their tin in a blender or food processor, then season with salt to taste.
For the relish, pop everything in a blender with a few spoonfuls of water, blitz until almost smooth, then season with salt – you want it to have a bit of texture.
To serve, spoon the beans on to a platter, pile on the tomatoes and any marinade that they haven’t soaked up, then drizzle the relish all over the top. Serve with lettuce leaves for wrapping, or on toast, or slathered on to charred flatbreads.
