Preheat oven to 350 degrees. Make the tomato sauce: Heat the olive oil in a medium saucepan set over medium heat. Add the onion and garlic, and cook, stirring frequently, until onion and garlic are browned, about 4 minutes. Add the dried oregano, dried basil, crushed red pepper flakes, bay leaf, chopped tomatoes, and tomato paste. Bring mixture to a boil. Reduce heat to medium-low, and let simmer, stirring occasionally, until the liquid has evaporated and the sauce is thick, about 35 minutes.
Assemble the pizzas: Arrange pita breads on two baking sheets. Spread about 6 tablespoons tomato sauce on each. Scatter strips of yellow bell pepper on top, and then sprinkle with the mozzarella cheese. Transfer the baking sheets to the oven, and bake the pizzas until the peppers begin to wilt and the mozzarella has melted, about 20 minutes. Remove the pizzas from the oven, and transfer to a cutting board. Sprinkle with basil, and
cut each pita pizza into 12 wedges. Serve warm or at room temperature.