If you are going to cook your own beans, it’s best to soak them overnight or at least for few hours. Cook until beans are tender but do not add salt. Once ready, drain them and set aside to cool. For the dressing, put the garlic and rosemary in olive oil in a small saucepan. Heat on medium until the rosemary begins to sizzle. Remove the pan from the heat and let sit for 20 minutes, allowing the rosemary and garlic to infuse in the oil. Remove rosemary sprig and garlic clove from the oil and discard. In a medium bowl combine the beans with basil leaves, onions and tomatoes, and season with salt. Let sit for a few minutes for the beans to absorb the salt and flavors of other ingredients. Gently mix in the infused olive oil and serve.