Preheat the oven to 420ºF.
Transfer the tomatoes, garlic, and onion to a large casserole or baking dish.
Roast for 35 minutes or until the tomatoes have softened and the onion is golden brown.
Transfer the tomatoes and onion to a large nonreactive saucepan (ceramic or stainless steel), or to a blender. Squeeze the garlic cloves from their skin and into the saucepan.
Add the beans, vegetable broth, maple syrup, nutritional yeast, and basil. Blend using an immersion blender or in a blender until smooth. (Transfer to a large saucepan if using a blender).
Heat over medium-high heat until warmed through, adding more broth, and seasoning as desired. Add oat milk for a creamier texture as needed. Garnish with fresh basil for serving.