Preheat your cast iron skillet over medium heat.
Add butter and let it melt.
Add the sliced zucchini and season with garlic powder, salt, and pepper.
Cover with a lid and cook for about 5–7 minutes, stirring occasionally, until the zucchini is tender and lightly browned. (Keeping the lid on helps it steam and soften while still browning underneath.)
Remove the lid for the last couple minutes to allow any moisture to cook off.
Taste and adjust seasoning. Garnish if desired.