Place potatoes in microwave-safe bowl and cover with plastic wrap. Cook 5-8 minutes, stirring once. Cool for 1 minute.
While potatoes are cooking, melt butter in a cast iron skillet over medium heat. Add peppers and onions and sauté until tender, about 5 minutes. Add garlic and cook for one more minute.
When the potatoes are cool enough to handle, slice them into 4 pieces each. Add the potatoes to the skillet and gently stir until coated. Sprinkle with salt and pepper. Sauté over medium heat until lightly browned on cut sides, about 5-8 minutes.