Heat the oven to 375°F. Warm 1 teaspoon of the olive oil in a skillet over medium heat. Add the diced onion and cook for 4 to 5 minutes, stirring occasionally, until softened. Set aside to cool slightly.

In a mixing bowl, combine the ground turkey, egg, breadcrumbs, milk, cooked onion, ½ teaspoon of the thyme, ½ teaspoon of the salt, and the black pepper. Mix gently until just combined. Shape the mixture into a loaf and place it in a baking dish.

In a small bowl, whisk together the apple cider, Dijon mustard, maple syrup, and apple cider vinegar. Spoon about half of the glaze over the meatloaf, spreading it across the top.

Bake for 30 minutes. Spoon the remaining glaze over the loaf, then bake for another 15 to 20 minutes, until the center reaches 165°F. Let the meatloaf rest for 5 minutes before slicing.

While the meatloaf bakes, heat the remaining olive oil in the skillet over medium heat. Add the sliced cabbage, remaining ¼ teaspoon of thyme, and remaining ¼ teaspoon of salt. Cook for 10 to 15 minutes, stirring now and then, until tender with a few lightly browned edges. Serve alongside the sliced meatloaf.