Cook 1 bunch of trimmed and halved radishes and 1 sliced red onion in a skillet with olive oil over medium-high heat, stirring, until tender, about 8 minutes. Season with salt and pepper. Stir in 5 ounces baby spinach, the juice of 1/2 lemon, and a pinch each of salt and pepper. Cook until wilted, about 1 minute. Plate!