Preheat oven to 350°F (180°C).
Wash and dry potatoes, then chop into small pieces. Place into a pot of cold, salted water and bring to a boil. Reduce heat and cook potatoes for 5 minutes, until fork tender. Remove from heat, drain and set aside.
To make black bean spread: Combine half of the black beans and half of the roasted red peppers with salt, Mexican chili powder and garlic in a food processor. Puree until smooth. Set aside.
Spread the black bean and roasted red pepper mixture evenly on the flatbread, leaving a ¼-inch border. Scatter with potatoes, remaining black beans and roasted red peppers, then sprinkle with cheese and jalapeño.
Transfer to a baking sheet lined with parchment paper and place into the oven. Bake for 20 minutes until flatbread is crisp and cheese is melted. Remove from the oven and transfer to a cutting board. Garnish with green onions and cilantro. Cut into 8 slices and serve warm.