Begin by lightly boiling the beans in a pan of salted boiling water, they should take around 3 minutes to cook. Once tender, remove from the heat, drain and then run under cold water to cool them down.
Next, prepare the onions and tomatoes and adding them to a mixing bowl along with the remaining ingredients. Add in the cooled beans and then give everything a good stir to combine all the flavours.
Taste for seasoning before adding salt and pepper as the capers can be quite salty.
Delicious as a side salad or maybe on some toasted sourdough.