Steam potatoes – if thin skinned and blemish free there is no need to peel.
Steam green beans, then blanche
Slice red onions – rinse with cold water then drop into vinegar
Put vinegar into a large bowl. Whisk in Dijon mustard, and ½ teaspoon salt.
Slice potatoes in half and add to bowl while still warm. The potato will absorb the vinegar and mustard when it is warm.
Slice red onion into half moons
When green beans are tender drop them into ice water to retain their color. Blot them on a paper towel and then into the bowl with the potatoes and onions.
Add olive oil.
Halve tomatoes and drop into bowl.
Stir and taste. Adjust seasoning.
Recipe by Make Mine Lemon at https://www.makeminelemon.com/potatoes-and-green-beans/