1. Warm oil in a large nonstick skillet over medium-high heat. Add shallots and cook, stirring frequently, until wilted, about 5 minutes. Add asparagus and continue to cook, tossing frequently, until asparagus is crisp-tender, 5 to 7 minutes longer.

2. Add radishes, lemon zest and butter to skillet; season with salt and pepper. Cook, stirring often, until radishes are just warmed through, about 1 minute. Squeeze lemon juice over and toss again. Season with additional salt and pepper, if desired. Serve immediately.