Preheat your oven to 400°F. Slice the tomatoes and prepare the onion and other ingredients. Having everything ready makes the cooking process smooth and stress-free.
Place the sliced tomatoes in a baking dish. Drizzle with olive oil and season with salt and pepper. Roast until they become tender and slightly caramelized.
Heat olive oil in a large pot over medium heat. Add the onions and a pinch of salt. Cook until soft and lightly golden for extra flavor.
Add the white beans, sun-dried tomatoes, tomato paste, garlic powder, and oregano to the pot. Stir well so everything combines evenly.
Add the roasted tomatoes along with their juices. Stir in parsley, olives, spinach, and lemon juice. Cook until the spinach wilts and everything is heated through. Adjust seasoning and consistency if needed.
Taste and adjust salt, pepper, or lemon juice. Serve immediately while warm and comforting.