Preheat the oven to 350°F.
Add the tomatoes to a small baking sheet lined with parchment paper. Drizzle 1 tablespoon of olive oil over the top and sprinkle with salt. Place in the oven and bake for 10 minutes. Remove from the oven and transfer the tomatoes to a warm dish. Set aside.
Heat the remaining 1/4 cup olive oil in a large pot over medium heat. Add the onion and garlic and cook for 5 minutes to soften. Add the beans and cook, stirring occasionally, 5 minutes longer. Add the artichoke hearts and pour the water into the pot. Season with salt and pepper and bring to a boil. Reduce the heat to low, cover, and simmer for 20 minutes. Remove from the heat.
Using an immersion blender, carefully, puree the soup to your desired consistency. Stir in the lemon juice and reheat over medium heat. Taste for seasoning and season with salt and pepper, if desired. Remove from the heat.
Divide the soup into individual bowls. Arrange some of the red onion and tomatoes in the center of the soup. Sprinkle with the thyme leaves and drizzle with a little bit of olive oil. Serve immediately.