- Preheat the oven to 180 degrees.
- Wash the potatoes, cut into quarters or eighths, depending on size.
- Peel the onion, cut into thin strips and add to the potatoes.
- Wash the rosemary, picking off the needles and adding them to the vegetables.
- Mix the ingredients for the marinade well in another bowl, mix with the potatoes and place on a sheet of baking paper.
- Bake for about 15-20 minutes and serve.