Peel and dice potatoes.
Add potatoes to a large bowl filled with water (keeps them from turning brown while you peel and dice the rest of the potatoes).
In a large frying pan, add oil and heat over medium heat.
Drain water from potatoes and return to bowl. Add bell pepper, onion, garlic, jalapeño, cayenne pepper, salt and pepper. Mix well.
Gently add some potatoes to oil and cook until crispy and golden brown.
Add chopped tomatoes when potatoes are almost done.
If you are using a large frying pan, you might be able to cook all of them at once. If not, place cooked potatoes on a plate lined with paper towels and cook the remainder of the potatoes until golden brown and crispy. Cooking time will vary.