Preheat your oven to 220 °C / 430 °F. Peel and dice the onion. Cut the pancetta or bacon into small cubes. Place a skillet with olive oil over medium-high heat. Add diced onion and pancetta or bacon. Cook for 5 minutes, stirring occasionally. Meanwhile, prepare the sauce. In a bowl, stir to combine diced tomatoes, brown sugar, vinegar, and water. When the onion is softened, add the diced garlic, paprika, oregano, and bay leaf. Gently season with pepper, stir and cook for another minute for the spices to release all the aroma.
cook the tomato sauce
Add the prepared tomato sauce to the skillet and bring to a boil. Simmer for about 15 minutes, or until the sauce thickens. Remove the bay leaf and add the drained white beans (like Cannelini). Bring to a boil, then simmer for 5 minutes. Season with salt and pepper.
Remove from the heat and transfer to a deep baking dish. Place the baking dish on a baking sheet to prevent spills. Place in the preheated oven on the middle rack. Bake for 20 - 25 minutes at 220 °C / 430 °F or until beautifully caramelized and cooked.
Toast six thick slices of white bread or toast bread. Divide between six plates and generously spoon the baked beans on top. Optionally sprinkle with chopped parsley and drizzle with olive oil.