Wash and cut green beans into 1-inch lengths.
Place in a small pot and add just enough water to cover the green beans, add green beans and salt, bring to a boil and cook for 2-3 minutes until beans have softened.
Drain and rinse under cold water set aside in a sieve to cool.
Drain baked beans and reserve the liquid (sauce).
Drain and rinse red kidney beans.
Finely chop onions, cutting some into long strips for garnishing.
Peel the cucumber and remove the seeds, chop into 1/2 inch cubes.
Remove seeds from the tomato, chop into 1/2 inch cubes.
Tear up the few leaves of lettuce.
Put everything in a bowl and mix.
Cover and place in the fridge for several hours or overnight to meld well.
Keep dressing separately in the fridge.
A few hours before serving, add enough dressing and mix well with the salad.