Prepare the red pepper. For best results you need to char and peel the pepper to give it a really soft texture. This can be done a number of ways; the best way (and most fun) is on a BBQ, but under a grill on a really high heat works equally well. Ensure that you keep turning the pepper once it starts to caremalise and char the skin - this takes around 10 - 15 minutes.
Once the skin has blackened, remove the pepper from the heat and allow to cool for a few minutes. Once cool enough to touch, slice the pepper in half, remove the seeds and membrane, and remove the skin. Finally slice the pepper into thin strips. Set aside.
Prepare and cook the potatoes. Peel the potatoes and slice into thin discs that are approximately 3mm thick. Place the discs into a pan (I needed 2 pans) on a low heat with 1tbsp of olive oil and fry for between 15 and 25 minutes, depending on the thickness and type of potatoes. You should be able to tell when the potatoes are cooked, as they will start to go soft and may even break up a little in the pan. Make sure that you keep turning the potatoes, otherwise they are likely to burn! Set aside.
Break the eggs into a bowl, season and whisk together with a fork until the egg whites and yolks are completely blended. Once blended, add in the potatoes, spinach and red pepper into the mixture and give it a good mix.
Preheat the grill in preparation, then heat 1 tbsp of oil in a frying pan and pour in the egg mixture. Using a wooden spatula, keep going around the edges of the pan and pushing the cooked egg into the middle. After 5 minutes, the omlette should be cooked around the edges and slightly wobbly in the centre. Remove the tortilla from the heat.
Crumble over the cheddar and feta cheese and place the pan under the grill for around 5-7 minutes, or until the egg is cooked through and the tortilla no longer wobbles.
Slice up the tortilla and serve luke warm with a fresh salad or in baguette.