Pre-heat the barbecue with the Paella Pan in place, or you can use the Chef Pan or a deep sided frying pan. Add a little rapeseed oil and add most of the onions, reserving a little for the salsa. Cook on a low heat for around 10 minutes until the onion has softened.
To make the salsa fry the onion and garlic gently for a few minutes, add the chilli then one minute later add the fresh tomatoes and peppers. Cook on a low-medium heat for a couple of minutes then add the chopped tomatoes. Season with salt, pepper and a pinch of sugar, then cover and cook on a low heat for about 20 minutes until it has reduced and thickened. Taste and season accordingly.
While your onions cook whisk the eggs and season with salt and pepper. Slice the potatoes into thin slices, then lay out in the pan in a single layer. Cook for a minute or two then add in the whisked eggs, cover and leave to cook gently. After 20 mins, the edges and base should be golden, the top set but the middle still a little wobbly. To turn it over, slide it onto a plate and put another plate on top, turn the whole thing over and slide it back into the pan to finish cooking.
Once cooked, transfer to a plate and serve the tortilla warm or cold with some warm salsa on the side.