In a large pot, heat olive oil over medium-high heat. Add yellow and red onion and salt, cover and cook, stirring occasionally, until tender, 6-8 minutes.
Add garlic and cook until fragrant, about 30 seconds.
Add wine and simmer until evaporated, 3-5 minutes.
Add cauliflower and chicken broth, stir and bring to a boil. Reduce heat to medium-low, cover and simmer until vegetables are very tender, about 20 minutes.