Preheat your oven to 200 ° C.
Brush your baking dish with some oil.
Peel and wash your potatoes, and cut into thin slices or medium-small cubes, and pat them dry.
Chop your onion in slices too.
Place your potatoes, and onion in a large bowl, add the olive oil, garlic powder, salt, pepper, thyme, and mix.
Transfer them to the oiled baking dish and place in the preheated oven, and bake for approximately 20-25 minutes.