Potatoes with Onion, Tomato and Sweet Pepper

From Marcella Hazan's Essentials of Classic Italian Cooking.
1 sweet bell pepper
2 cups onion sliced thin
1/3 cup extra virgin olive oil
1 1/2 tomatoes, peeled and chopped
Black Pepper
1 1/2 pound waxy boiling potatoes
1. Remove seeds from pepper, peel and cut lengthwise into 1/2 inch wide strips
2. Choose a saute pan that can accommodate all the ingredients, put in the onions and olive oil, and turn to heat to medium. Cook, stirring until the onions wilt and become light gold, then add pepper. Cook for 3-4 min, stirring occasionally, then add tomatoes with their juice, adjusting the heat to cook at a slow, but steady simmer.
3. While tomatoes are cooking, peel the potatoes, wash them in cold water, and cut into 1-inch cubes.
4. When the oil floats free of the tomatoes, add the potatoes, turn the heat down to very low, and cover the pan. Cook until the potatoes feel tender when prodded with a fork, about 30 minutes, depending on the potatoes. While cooking, turn the contents of the pan over from time to time. Add several grinding of pepper and correct for salt.