1. Make oven roasted tomatoes: Preheat the oven to 400ºF. Brush the tomatoes with olive oil, salt and rosemary. Place in the oven and roast for 12 minutes. Remove and set aside.
2. Make balsamic onions: Slowly cook the onions in the olive oil over low heat until softened. Add the vinegar and continue cooking for 3 minutes. Remove from heat and set aside.
3. Make blue cheese topping: Using a fork, combine the blue cheese, walnuts, scallions, parsley and ricotta cheese.
4. Make the flatbread: Brush the bread with olive oil and season with Parmesan cheese and salt. Toast in the oven for about 10 minutes.
5. Remove and immediately top with balsamic onions, tomatoes and Castello® Crumbled Blue Cheese. Cut the flatbread into triangles and serve while warm or room temperature.