A crisp and refreshing salad combining steamed green beans, cannellini beans, and dark red kidney beans with thinly sliced fennel and sweet onion. The homemade Dijon and red wine vinegar dressing brings a bright tang that ties the earthy legumes and aromatic fennel together. It makes a perfect make-ahead side dish for picnics or weeknight dinners, as the flavors deepen after a short rest in the fridge.