Prep the onions. Preheat the oven to 200 °C / 400 °F. In a baking dish, stir together the onions, rosemary, paprika, salt, olive oil and ½ cup of the broth until the onions are evenly coated. Nestle the garlic bulb, cut side up, in the middle of the dish.
3 large white onions, 1 bulb garlic, 1 tsp dried rosemary, 2 tsp sweet paprika, 2 tbsp olive oil, 4 ½ cup vegetable broth, divided, ½ tsp salt