Fill a medium saucepan one-third full of water; add 1/4 teaspoon salt. Coarsely chop unpeeled potatoes by slicing lengthwise into strips, then cutting crosswise. Place potatoes in saucepan. Bring water to boiling over high heat; reduce heat. Cook, uncovered, for 5 minutes. Remove from heat; drain well. In a medium bowl combine potatoes, onions, jalapeno pepper (if using), the remaining 1/4 teaspoon salt, and pepper (if using).
In a large nonstick skillet melt butter. Add potato mixture and cook over medium heat, turning occasionally, about 20 minutes or until potatoes are soft and browned to your taste. Makes 4 servings.