Preheat oven to 200 degrees C. Par boil the potatoes in lots of water for about 10 minutes. Drain then place in a baking dish mix through half the olive oil some oil and salt and bake till cooked-about 20-30 mins, but check them.
Then make the sauce; fry the onion and garlic in some oil till transparent. Stir in the chilli powder and paprika. Then add the tomatoes and water (or the tin and its juice) and the vinegar or wine. Cook for about 20 minutes or until reduced a bit and it looks rich.
Blend the sauce in a blender or food processor till smooth. Add salt and pepper to taste.
Serve the potatoes in a dish with the sauce over it.