This salad is at its best when the fennel is sliced thin enough to bend but still snap between your teeth. Sweet orange and creamy white beans soften that crunch, while a mustardy citrus dressing makes the bowl feel complete. It serves two as a main or four alongside a larger meal.
Slice the fennel thin
Trim one medium fennel bulb, saving a few fronds for garnish, and slice the bulb as thinly as you can with a sharp knife or mandoline. Peel two oranges, cut away the white pith, and slice the fruit into rounds over a bowl to catch the juice. Rinse and drain one 15-ounce can of cannellini beans, then pat them dry.
Shake up the citrus dressing
Whisk two tablespoons of olive oil with one tablespoon of the reserved orange juice, one tablespoon of lemon juice, and one teaspoon of Dijon mustard. Season with salt and black pepper, then taste and add a little more lemon if the dressing seems too sweet. The mustard helps the oil and citrus stay together as you toss the salad.
Toss gently and serve
Combine the fennel, orange slices, and cannellini beans in a wide bowl, then pour over the dressing and toss gently so the orange keeps its shape. Finish with the reserved fennel fronds and, if you like, a few thinly sliced red onion rings. Let the salad sit for five minutes before serving so the beans pick up some of the citrus dressing.