Preheat your oven to 350°F (180°C). Prepare a baking sheet with aluminum foil for the garlic heads.

Slice off the tops of the garlic heads, drizzle with olive oil, wrap in foil, and roast for 60-90 minutes until golden brown.

Heat a tablespoon of olive oil in a large saucepan over medium heat. Sauté diced onions for about 5-7 minutes until translucent.

After garlic is roasted, squeeze cloves into the saucepan with sautéed onions. Stir and then add the vegetable broth, drained beans, and rosemary. Bring to a boil and simmer for 5 minutes.

Blend the soup using an immersion blender until silky-smooth. If using a countertop blender, blend in batches.

Stir in optional parmesan cheese and lemon juice. Adjust seasoning with salt and pepper before serving hot.