Melt butter in a Dutch oven over medium-high heat; add onion. Cook 4 minutes or until lightly browned, stirring occasionally. Add the cauliflower, potato, carrot, and caraway seeds. Cook 6 minutes or until cauliflower begins to brown, stirring frequently. Add broth; bring to a boil. Reduce heat; simmer 20 minutes or until vegetables are tender. Stir in salt and pepper.