Keep a kettle of boiling water nearby to easily refill the steamer pot.
Set a steamer basket inside a pot of water and bring to a boil. Working in batches, and refilling pot with water as needed, steam vegetables until crisp-tender, 3 to 5 minutes for broccolini; 4 to 5 minutes for asparagus, squash, and zucchini; 5 to 6 minutes for carrots; and 15 to 20 minutes for beets.
Arrange vegetables on a platter. Season with salt, drizzle with oil, and squeeze with lemon. Garnish with microgreens; serve.