Carrying this dish is easy: Stack the fillet slices together and wrap them in plastic wrap; pack the arugula, onions, beans, and dressing in separate containers. Prepare beans in boiling salted water up until crisp-tender, about 5 minutes. Include oil in a sluggish stream, blending till emulsified., Cut beef into thin slices., Include onion pieces, beef, and enough dressing to arugula and beans to just coat and toss to combine well.
