Preheat the oven to 400°F (200°C) and lightly grease a medium casserole dish.

Put the prepared carrots and potatoes into the dish and spread in an even layer.

Mix the salt into the melted butter in a small bowl, then drizzle the butter mixture over the vegetables.

Toss the veggies in the casserole dish to ensure they're all evenly coated.

Cover tightly with aluminum foil and bake for 25-30 minutes to soften the vegetables.

Remove the foil (be careful not to burn your hands on the steam), toss the veggies to get them coated in the juices, and spread into an even layer again.

Continue baking uncovered for 25-35 minutes, until the vegetables are well-caramelized and golden-brown around the edges and completely tender when pierced with a fork.

Serve hot and spoon any butter juices from the bottom of the casserole dish over the top.