Peel the carrots and cut them into even 1/4-inch diagonal slices. If using small baby carrots, leave them whole; larger baby carrots can be halved lengthwise if needed for even cooking.

Place the carrots in a saucepan and add enough water to barely cover them. Add a pinch of salt, bring the water to a boil, then reduce the heat and simmer for 8–12 minutes, until the carrots are nearly tender but not soft.

Drain the carrots well so excess water does not thin the glaze. Return the empty saucepan to medium heat and add the butter, brown sugar, orange juice, orange zest, 1/4 teaspoon kosher salt, and black pepper.

Simmer the orange-butter mixture for 2–4 minutes, stirring occasionally, until the butter melts and the liquid begins to reduce. This short reduction concentrates the citrus flavor and helps the finished glaze cling to the carrots.

Add the drained carrots to the saucepan and toss gently to coat. Cook for another 3–5 minutes, stirring carefully, until the carrots are tender and covered in a glossy orange glaze.

Transfer the carrots to a serving dish and sprinkle with the chopped fresh parsley, if desired. Serve hot while the glaze is shiny and the carrots are at their most tender.